Law & Ethics: Authorization, Scope & Rules of Engagement

This is Chapter 5 of the Security Foundations series — Notebook 8. Chapter 4 mapped the industry as a set of jobs. This chapter covers the thing every one of those jobs is built on: the document, the signature and the boundary that make your work legal.

Here is the uncomfortable truth that this chapter exists to make concrete. The packets an attacker sends and the packets a paid penetration tester sends are frequently byte-for-byte identical. There is no technical property of a TCP SYN, an HTTP request, or a sqlmap payload that marks it as authorized. Nothing in the protocol carries consent. The entire difference — the difference between an invoice and an indictment — lives in a piece of paper, a scope definition, and whether the person who signed it had the authority to sign it.

That asymmetry is why this is not a boring compliance chapter to skim. It is the highest-consequence material in the entire notebook. A misconfigured nmap command against a /16 you did not verify can end a career. A scope line that says “*.example.com” without qualification can put you on a shared hosting provider’s infrastructure that belongs to three hundred other companies. Getting this right is a skill with its own techniques, its own tooling, and its own hands-on practice — and that is exactly how it is taught here.

A necessary disclaimer, stated once and meant throughout. This chapter is educational material written by a security practitioner, not legal advice, and it is not a substitute for a lawyer. Laws differ by country, by state, by sector and by contract, they change, and their application depends on facts this chapter cannot know. Everything here is a framework for asking better questions and for recognising when you need counsel — not a determination that any specific activity is lawful. When real money, real production systems or real risk are involved, get a real lawyer.

Part 1: The Authorization Principle — Why a Packet Has No Legality

Start with the mental model that everything else in this chapter hangs from.

Computer crime statutes around the world converge on a single conceptual core: it is an offence to access a computer system without authorization, or to exceed the authorization you were given. The wording varies — “without authorisation” in the UK, “without authorization or exceeding authorized access” in the US, “without permission of the owner” in India — but the load-bearing word is always some form of authorization.

Notice what is absent from that formulation. There is no requirement that you caused damage. There is no requirement that you had malicious intent, in many jurisdictions. There is no exemption for curiosity, for research, for “I was going to report it,” or for “the system was obviously misconfigured.” Those things can matter enormously at the charging and sentencing stage, and modern prosecutorial policy in several countries explicitly considers them — but they are mitigations, not the definition of the offence. The offence is the unauthorized access itself.

flowchart TD
    A[You send a packet to a system] --> B{Do you have<br/>authorization?}
    B -->|No| C[Potential criminal offence<br/>regardless of intent or damage]
    B -->|Yes| D{Is this specific action<br/>inside the granted scope?}
    D -->|No| E[Exceeding authorized access<br/>still potentially an offence]
    D -->|Yes| F{Was the authorization<br/>given by someone with<br/>the authority to give it?}
    F -->|No| G[Invalid consent<br/>you are unauthorized]
    F -->|Yes| H{Is it still valid?<br/>in date, not revoked,<br/>asset still owned by them}
    H -->|No| I[Authorization lapsed<br/>stop immediately]
    H -->|Yes| J[Lawful testing]
    J --> K[Document everything<br/>as you go]

Four gates, all of which must be open simultaneously: authorization exists, the action is in scope, the grantor had authority, and the grant is currently valid. A failure at any one gate puts you outside the law even if the other three are perfect. Most real-world incidents involving well-intentioned testers are gate-three or gate-four failures — a scope signed by someone who did not own the asset, or an engagement that ran past its authorized window.

Why this matters even if you never do a paid pentest. Bug bounty hunters operate under a unilateral grant of authorization published by the program owner; if you step outside its terms, the grant does not cover you. CTF players operate under the event’s terms of service, and pivoting from a CTF box to the hosting provider’s infrastructure has ended more than one competitor’s participation and worse. Blue teamers who “test the detection” against a partner network are equally exposed. The principle is universal.

1.1 The Two Failure Modes: No Authorization vs. Exceeded Authorization

These are legally distinct and worth separating in your head.

No authorization at all is the simple case: you scanned a host you have no relationship with. This is the classic “I ran masscan against the internet to build a research dataset” scenario, and it is also the most commonly prosecuted.

Exceeding authorized access is the subtle and far more dangerous case for professionals, because it happens inside an engagement you were legitimately hired for. Examples that have caused real trouble:

• Testing 10.0.0.0/8 when the scope said 10.10.0.0/16, because of a typo in an nmap target file.
• Using credentials issued for the staging environment against production because SSO silently spanned both.
• Pivoting from an in-scope web server into a database host that was never listed, on the reasoning that “demonstrating impact requires it.”
• Continuing to test after the engagement window closed because you wanted to finish a promising lead.
• Downloading a full customer database to “prove” the SQL injection, when a single row count would have proved it.

That last one is worth dwelling on, because it is the single most common way competent testers create legal and contractual exposure for themselves. Proof of vulnerability is not the same as maximum exploitation. The professional standard is minimum sufficient demonstration — see Part 10.

1.2 A Sequence That Shows Where Consent Actually Lives

sequenceDiagram
    participant C as Client (asset owner)
    participant L as Client legal / procurement
    participant T as Testing team
    participant SOC as Client SOC / blue team
    participant S as Target systems

    C->>L: Requests security assessment
    L->>T: MSA + NDA signed
    T->>C: Scoping questionnaire
    C->>T: Asset inventory + ownership attestation
    T->>C: SOW + Rules of Engagement draft
    C->>T: Signed SOW, ROE, Authorization Letter
    Note over T,C: Authority verified: signer owns or controls assets
    T->>C: Source IPs, test window, emergency contacts
    C->>SOC: Deconfliction brief (do NOT allow-list, just log)
    T->>T: Independent scope validation (Part 9)
    T->>S: First packet — only now
    S-->>T: Findings
    T->>C: Critical finding out-of-band, immediately
    T->>SOC: Deconfliction check on suspicious activity
    T->>C: Report + evidence handover + data destruction attestation

The single most important line in that diagram is T->>S: First packet — only now. Everything above it is the authorization. In a real engagement, that is typically two to six weeks of work before any technical activity begins, and the mature teams treat it as engineering work with the same rigour as the testing itself.

Part 2: The Legal Landscape — Statutes You Should Actually Know

You do not need to be a lawyer, but you must be able to recognise which statute governs the work you are doing and what its rough contours are. Here is the practitioner’s map.

Jurisdiction	Primary statute	Core prohibition	Notable feature for testers
United States	Computer Fraud and Abuse Act, 18 U.S.C. § 1030	Accessing a “protected computer” without authorization or exceeding authorized access	Van Buren v. US (2021) narrowed “exceeds authorized access” to a gates-up-or-down test; DOJ 2022 policy declines charging good-faith security research
United States (state)	State computer crime statutes (e.g. California Penal Code § 502)	Broadly parallel to CFAA, sometimes broader	State charges can follow even where federal charges are declined
United Kingdom	Computer Misuse Act 1990, ss. 1–3A	s.1 unauthorised access; s.2 access with intent to commit further offence; s.3 unauthorised acts impairing operation; s.3A supplying “hacking tools”	s.1 has no damage requirement and is very broad; s.3A has long worried tool authors
European Union	Directive 2013/40/EU, implemented in member-state law	Illegal access, illegal system/data interference, illegal interception	Recital allows member states to exempt authorised testing; implementation varies widely
India	Information Technology Act 2000, ss. 43, 65, 66	s.43 civil liability for access without permission of the owner; s.66 criminalises s.43 acts done dishonestly/fraudulently	s.43 is strict-liability civil — no intent needed for damages
Germany	Strafgesetzbuch § 202a–202c	Data espionage, interception, preparation of such acts	§ 202c (“Hackerparagraf”) criminalises preparing tools; interpreted narrowly by the Constitutional Court but still chills tooling
Australia	Criminal Code Act 1995, Part 10.7	Unauthorised access/modification/impairment of data	Carriage-service element gives it broad reach
Singapore	Computer Misuse Act (Cap. 50A)	Unauthorised access, modification, interception	Extraterritorial reach where the computer is in Singapore
Canada	Criminal Code s. 342.1, s. 430(1.1)	Unauthorised use of computer; mischief in relation to computer data	“Fraudulently and without colour of right” element
Japan	Act on Prohibition of Unauthorised Computer Access	Unauthorised access using another’s identification code, or bypassing access control	Access-control-bypass framing is unusually explicit

Two structural observations you should carry away from that table rather than the specifics.

First, jurisdiction is plural, not singular. A tester in Bangalore, hired by a company registered in Delaware, testing a web application served from AWS eu-west-1, with a database in Singapore, has potentially engaged four legal systems. The contract should specify governing law, but a contract between you and your client cannot bind a third-party prosecutor in a fourth country. When engagements cross borders — and cloud makes almost all of them cross borders — this is a question for counsel, not for you.

Second, “protected computer” and equivalent terms are enormous. Under the CFAA, a “protected computer” includes any computer “used in or affecting interstate or foreign commerce or communication.” In practice that is any internet-connected device on earth. Do not assume small, obscure, or personal systems fall outside these statutes.

2.1 Van Buren and the Gates-Up-or-Down Test

Because so much security work happens under US law or US-headquartered clients, one case deserves real explanation.

In Van Buren v. United States (2021), the US Supreme Court considered a police officer who used his legitimate access to a licence-plate database to look up a plate for an improper, non-law-enforcement reason. The government argued this “exceeded authorized access” under the CFAA, because he had access for some purposes but not that one.

The Court rejected that reading. It adopted what commentators call the gates-up-or-down test: the CFAA covers obtaining information from areas of a computer that are off limits to you, not obtaining information you are allowed to reach but for a purpose the owner would dislike. If the gate is up for you, walking through it is not a CFAA violation even if your motives are bad.

Why this matters enormously for security research:

• Terms-of-service violations alone are much weaker as a CFAA theory. Scraping a publicly accessible page in violation of a robots.txt or a ToS clause is, post-Van Buren, far harder to charge as unauthorized access.
• Technical access controls became the dividing line. If you bypass authentication, guess an ID to reach another user’s record (IDOR), or defeat rate limiting designed as a barrier, you are pushing through a gate that was down for you. That is squarely inside the statute.
• It did not legalise research. The Court expressly left open questions about what counts as a gate. And it says nothing about state statutes, contract law, or other countries.

The practical rule for a tester: Van Buren narrows one theory of liability. It does not create a research exemption, and no competent professional relies on it as a substitute for written authorization.

2.2 The DOJ Charging Policy for Good-Faith Research

In May 2022, the US Department of Justice announced a policy directing federal prosecutors not to charge good-faith security research under the CFAA. It defines good-faith research roughly as accessing a computer solely for purposes of good-faith testing, investigation, or correction of a vulnerability, where the activity is carried out in a manner designed to avoid harm to individuals or the public, and where the information derived is used primarily to promote security or safety.

Understand precisely what that is and is not:

• It is an internal charging policy, not a statute and not a court ruling. It can be revised by a future administration without any legislative act.
• It binds federal prosecutors only. State attorneys general, foreign prosecutors, and private civil plaintiffs are unaffected.
• It contains a large carve-out: activity is not good faith if it is “in pretext of good-faith research” — for example, discovering a flaw and then extorting the owner, or selling it to a party that will misuse it.
• Civil liability is untouched. A company can still sue you under contract, trade secret, or state law.

Protection mechanism	What it actually is	Binding on prosecutors?	Binding on civil plaintiffs?	Can be revoked?
Signed authorization letter	Contract + consent	Strong evidence of authorization	Yes, if drafted well	Yes, by the client — get it in writing
Bug bounty safe harbour	Unilateral public promise / licence	Persuasive, not binding	Usually yes, if it says so	Yes, program terms change
DOJ 2022 charging policy	Executive branch policy	Directive to federal prosecutors	No	Yes, by policy change
Van Buren holding	Judicial interpretation of statute	Yes, courts must follow	Yes for CFAA civil claims	Only by legislation or later ruling
DMCA § 1201 security research exemption	Triennial Copyright Office rule	Narrow, anti-circumvention only	Partially	Yes, must be renewed every three years

The hierarchy is simple: a signed contract with the actual asset owner is worth more than every other row in that table combined. Everything else is a fallback you hope never to need.

2.3 Adjacent Statutes That Bite Unexpectedly

Computer crime law is not the only exposure. These come up constantly in real engagements.

• Wiretap / interception law. Capturing traffic that includes other people’s communications can trigger interception statutes (US Wiretap Act, UK Investigatory Powers Act, India IT Act s.66E for privacy violation). Running a rogue AP or an ARP-spoofing MitM on a corporate network you are testing is authorized only if the ROE explicitly says so, and even then employee communications may need separate handling. This is why “passive traffic capture” belongs in the ROE as an explicit, named-and-consented activity, not as an assumed part of network testing.
• Data protection law. GDPR Article 32 requires “a process for regularly testing, assessing and evaluating the effectiveness” of security measures — meaning pentesting is arguably mandated. But if your testing touches personal data, you are processing it, and you need a lawful basis, a data processing agreement, and often a defined retention and destruction schedule. India’s DPDP Act and similar regimes create parallel obligations.
• Sector regulation. PCI DSS Requirement 11 mandates internal and external penetration testing at defined intervals with defined methodology. HIPAA’s Security Rule requires risk analysis. DORA in EU financial services introduced threat-led penetration testing obligations (TLPT/TIBER-EU). These regimes shape what the test must cover, and misrepresenting a test as compliant when it was not is its own problem.
• Export control. Some intrusion-software and cryptography tooling is export-controlled (Wassenaar Arrangement implementations, US EAR). Shipping an implant or an exploit across a border can be a licensing question.
• Anti-circumvention. DMCA § 1201 in the US criminalises circumventing technological protection measures. The Copyright Office grants a renewable security-research exemption, but it is narrow and conditional.

Part 3: Who Can Actually Say Yes — The Authority Problem

Gate three from Part 1 is the one that fails most often and most quietly. Someone gives you permission. They are enthusiastic, senior-sounding, and completely lacking in the authority to give it.

Consent must come from the party with the legal right to control the asset. That is usually the owner, or someone with delegated authority from the owner. It is not:

• A developer who built the application but does not own the company.
• A friendly IT manager at a subsidiary, for assets owned by the parent.
• A customer of a SaaS product, for the SaaS provider’s infrastructure.
• A tenant of a shared hosting provider, for the shared server.
• Anyone at all, for a third-party dependency their app happens to call.

Scenario	Who you think can consent	Who actually must consent	Why
Company’s self-hosted web app on their own VPS	CISO	CISO (+ hosting provider ToS check)	They own the app and the VM; provider still has an AUP
App on AWS/Azure/GCP	CISO	CISO, within the provider’s published testing policy	Provider owns the underlying infrastructure
Salesforce/Workday/Okta tenant	Client	The SaaS vendor	Client owns data, vendor owns the system
Subsidiary’s network, parent-company contract	Parent CISO	Parent, if corporate structure grants control — verify	Separate legal entities may need separate consent
Third-party API the app calls	Client	The API provider	Client has no authority over someone else’s service
Payment gateway integration	Client	Gateway provider (and PCI constraints)	Out of scope by default
Shared hosting / cPanel	Client	Hosting provider	Other tenants share the host
Employee BYOD device	HR/IT	Employee + legal, per local employment law	Personal property and personal data
An acquired company mid-acquisition	Acquiring CISO	Depends entirely on deal close status	Pre-close, the target is still a separate entity
CDN / WAF in front of the app	Client	Usually the CDN vendor for the edge itself	Cloudflare, Akamai, Fastly have their own policies

3.1 The Verification Habit

Do not merely ask “do you have authority?” — that question gets a yes from everyone. Instead, build the answer from artefacts:

1. Ask for the asset inventory in writing, with an explicit ownership attestation clause signed by the client. Wording along the lines of: “Client represents and warrants that it owns or has the contractual right to authorise security testing of each asset listed in Appendix A, and will indemnify Tester for claims arising from any asset listed in error.”
2. Verify independently anyway. Ownership attestations are routinely wrong — not maliciously, but because nobody at a 5,000-person company knows every IP. Part 9 is a full lab on doing this.
3. Escalate the signature. The signer should be someone whose job title plausibly carries the authority: CISO, CTO, General Counsel, VP Engineering. A signature from a security analyst is not worthless, but it is weaker if the engagement goes wrong.
4. Re-verify at the start of each engagement, even with a repeat client. IP ranges get returned to the provider, domains lapse, subsidiaries get divested. An attestation from eighteen months ago is not evidence about today.

Red team usage: the authority problem is also an attack surface — an attacker who can convince a helpdesk they have authority gets access without exploiting anything. Social-engineering engagements probe exactly this. But the pretext used in an authorized social-engineering test is itself an activity that must be explicitly authorised in the ROE, and impersonating law enforcement or a government official is illegal in most jurisdictions regardless of what the ROE says. No contract can authorise an act that is independently criminal against a third party.

3.2 The Non-Delegable Limit

That last point generalises into a rule worth memorising: a client can only authorise you to do things to the client. A signed ROE cannot make it lawful to:

• Impersonate a police officer, government agency, or court.
• Access a third party’s systems, even to reach the client.
• Intercept communications of people who have not consented, where local law requires their consent.
• Violate export control by shipping tooling across a border.
• Damage property belonging to a landlord rather than the client (physical engagements).
• Test a system the client rents but does not control, without the owner’s consent.

If a client asks for any of these, the correct response is to explain why it cannot be scoped and to propose the lawful equivalent — e.g. replacing “impersonate the tax authority” with “impersonate a generic external vendor,” which tests the same human control without the criminal element.

Part 4: Scope — The Document That Defines Your Universe

Scope is the single most consequential technical artefact in the engagement. It is also, in most organisations, written badly.

A scope is not a paragraph. It is a structured, machine-readable-ish enumeration of exactly what may be touched, expressed in the same terms your tooling consumes.

4.1 Anatomy of a Good Scope Definition

# scope.yaml — the authoritative engagement scope
engagement:
  id: "ENG-2291"
  client: "Contoso Retail Holdings Ltd"
  authorized_by: "J. Okafor, CISO — signed authorization letter ENG-2291-AUTH-v3"
  window_start: "2026-04-06T09:00:00+01:00"
  window_end:   "2026-04-17T18:00:00+01:00"
  timezone: "Europe/London"

in_scope:
  ipv4:
    - "203.0.113.0/26"          # DMZ, client-owned, ARIN-verified
    - "198.51.100.14"           # legacy mail relay
  ipv6:
    - "2001:db8:4::/48"
  domains:
    - "shop.contoso-retail.example"
    - "api.contoso-retail.example"
  wildcards:
    - pattern: "*.stage.contoso-retail.example"
      note: "Wildcard limited to hosts resolving into 203.0.113.0/26 ONLY"
  urls:
    - "https://shop.contoso-retail.example/*"
  mobile:
    - platform: "android"
      package: "example.contoso.shop"
      version: "8.4.1"
  cloud:
    - provider: "aws"
      account_id: "111122223333"
      services: ["ec2", "alb", "s3"]
      note: "Provider policy permits; no simulated DoS, no other accounts"

out_of_scope:
  explicit:
    - "*.corp.contoso-retail.example"   # internal AD, separate engagement
    - "203.0.113.200"                   # third-party managed SIEM appliance
    - "payments.contoso-retail.example" # PSP-hosted, not client-owned
    - "Any host not resolving into the ranges above at time of test"
  activities:
    - "Denial of service, volumetric or application-layer"
    - "Physical intrusion"
    - "Social engineering of any kind"
    - "Modification or deletion of production data"
    - "Exfiltration of more than 3 records to demonstrate impact"
    - "Testing outside the declared window"
    - "Pivoting into any host not explicitly listed"

constraints:
  source_ips: ["192.0.2.44", "192.0.2.45"]
  max_request_rate: "20 req/s per host"
  user_agent_marker: "ENG-2291-PENTEST"
  credentials_provided: ["pentest_user_01", "pentest_admin_01"]
  no_test_hours: ["Fri 16:00-18:00 (weekly batch run)"]

escalation:
  critical_finding_contact: "+44 20 7946 0000 / soc@contoso-retail.example"
  emergency_stop_phrase: "HALT ENG-2291"
  deconfliction_contact: "blue-team@contoso-retail.example"

Every line in that file exists because its absence has caused a real problem somewhere. Walk through the ones that matter most.

user_agent_marker. Every HTTP request the team sends carries a unique, agreed string. When the SOC sees suspicious traffic at 03:00, they grep for ENG-2291-PENTEST and know in seconds whether it is you. This one line prevents more unnecessary incident escalations than any other control. In Burp, set it under Settings → Sessions → Match and Replace; in ffuf, -H "User-Agent: ENG-2291-PENTEST"; in nuclei, -H "User-Agent: ENG-2291-PENTEST".

source_ips. Fixed, declared egress addresses. The blue team logs them. Note the subtlety in Part 14: they should be logged, not allow-listed, or you are testing a fantasy environment.

The wildcard qualification. *.stage.contoso-retail.example is a trap without the resolution constraint. DNS is not ownership. If the client has a dangling CNAME pointing old.stage.contoso- retail.example at an S3 bucket now owned by someone else, an unqualified wildcard tells you to attack a stranger’s bucket. Bind wildcards to verified IP ranges.

max_request_rate. Rate limiting is not politeness, it is availability protection. A default sqlmap run with --threads 10 against a fragile legacy app is functionally a denial-of-service attack, and DoS is out of scope.

Exfiltration limits as a number. “Demonstrate impact without excessive data access” is unactionable. “Three records” is a rule you can follow and a rule an auditor can check.

4.2 Scope Ambiguity Patterns and Their Fixes

Ambiguous scope text	Why it fails	Correct replacement
“Our external perimeter”	Undefined set; changes daily	Explicit CIDR list + resolution-time constraint
“*.example.com”	Includes third-party SaaS on subdomains, dangling records	Wildcard + “must resolve into listed CIDRs at test time”
“The web application”	Excludes/includes API? Mobile backend? Admin panel?	Enumerated URL prefixes and host list
“All company assets”	Includes employee laptops, personal devices, acquisitions	Enumerate; exclude BYOD and unclosed acquisitions
“Production is out of scope”	Staging often shares a database with production	Name the boundary at the data layer, not the label
“No DoS”	Everyone agrees; nobody defines the threshold	Rate limits, thread caps, forbidden tool flags
“Test the AWS environment”	Which accounts? Which regions? Shared services?	Account IDs, region list, service list
“Internal network”	RFC1918 space overlaps with VPN pools, partner links	Exact VLANs/CIDRs, plus explicit exclusions
“During business hours”	Whose timezone? Whose holidays?	ISO 8601 timestamps with offset
“Report critical issues immediately”	“Immediately” and “critical” both undefined	Severity rubric + contact + SLA in hours

4.3 The Resolution-Time Problem

A subtle issue that catches experienced testers. Scope says shop.contoso-retail.example. You resolve it on Monday: 203.0.113.20, in scope. You run a long scan Wednesday night. In between, the client’s DevOps team moved the site to a new CDN, and shop.contoso-retail.example now resolves to an IP belonging to a CDN vendor with a strict no-testing policy — and possibly shared with other customers.

The fix is procedural, not clever. Re-resolve every hostname at the start of every test run, verify the result is inside the authorized IP ranges, and abort if it is not. The Python validator in Part 9.4 does exactly this, and it belongs in your run script, not in your head.

Part 5: Rules of Engagement — The Operational Contract

If scope answers what, Rules of Engagement answer how, when, and what happens when something goes wrong. It is the operational half of the authorization.

stateDiagram-v2
    [*] --> PreEngagement
    PreEngagement --> Scoping: NDA + MSA signed
    Scoping --> Authorized: SOW + ROE + Auth letter signed
    Authorized --> Validation: Independent scope verification
    Validation --> Scoping: Ownership unverifiable — renegotiate
    Validation --> Testing: All assets verified
    Testing --> Paused: Emergency stop invoked
    Paused --> Testing: Client clears resumption in writing
    Paused --> Terminated: Client halts engagement
    Testing --> CriticalEscalation: Critical finding / prior compromise
    CriticalEscalation --> Testing: Client acknowledges, testing continues
    CriticalEscalation --> Terminated: Client converts to IR
    Testing --> Reporting: Window closes
    Reporting --> Retest: Fixes deployed
    Retest --> Closure
    Reporting --> Closure: No retest contracted
    Closure --> [*]: Data destruction attested
    Terminated --> Closure

5.1 The ROE Parameter Reference

ROE parameter	Question it answers	Failure mode if omitted
Test window (with timezone)	When may packets fly?	Testing during a change freeze or peak trading
Source IPs	Where does traffic come from?	Blue team cannot deconflict; you get blocked
Traffic marker	How is our traffic identified?	Every alert becomes a full IR investigation
Rate limits / thread caps	How hard may we push?	Accidental DoS, contract breach
Permitted techniques	What classes of attack are allowed?	Disputes over phishing, MitM, password spraying
Forbidden techniques	What is explicitly banned?	Ambiguity resolved in the client’s favour, after the fact
Credential handling	What do we do with creds we find?	Cracked hashes stored insecurely; second breach
Data handling	How much data may we touch, where is it stored, when destroyed?	Regulatory exposure for both parties
Escalation path	Who do we call, how fast, for what severity?	Critical finding sits in a report for three weeks
Emergency stop	How does the client halt us instantly?	No way to stop a running scan during an outage
Deconfliction	How do we distinguish us from a real attacker?	Real intrusion attributed to the test and ignored
Evidence standard	What proof is required per finding?	Over-exploitation to “prove” impact
Retest terms	Is verification of fixes included?	Scope creep or unpaid work
Reporting format & delivery	Encrypted channel? Who receives it?	A pentest report emailed in plaintext
Third-party notification	Who tells the cloud provider / partners?	Provider AUP violation
Insurance	Who carries professional indemnity, at what limit?	Uninsured loss after an outage

5.2 Techniques That Must Be Named Explicitly

The default assumption should be that anything intrusive is out unless named in. These are the ones that most often cause disputes when left implicit:

• Password spraying and credential stuffing — can lock out real users; needs a lockout-policy discussion and often a “no more than N attempts per account per window” rule.
• Phishing / vishing / smishing — requires HR and legal sign-off, a defined target list, and a policy on what happens if someone enters credentials (you must not use them beyond agreed depth).
• Man-in-the-middle / ARP spoofing / rogue AP — intercepts third-party communications; wiretap exposure.
• Exploitation of confirmed vulnerabilities — some engagements are “identify only, do not exploit.” Know which you are on.
• Privilege escalation and lateral movement — an assumed part of red teaming, often forbidden in a standard pentest.
• Persistence mechanisms — if you install an implant, the ROE must cover installation, tracking, and guaranteed removal, with an inventory delivered at closure.
• Testing of third-party-managed devices — the managed SIEM, the outsourced firewall.
• Anything against Active Directory that writes — adding a machine account, modifying an ACL, and Kerberoasting all leave artefacts; some are trivially reversible, some are not.
• Data destruction, encryption or ransomware simulation — almost always simulate at the file-marker level only, never with real encryption.

Blue team usage: read the ROE from the defender’s side and you get a free gap analysis. Every technique the ROE forbids is a technique you will therefore have no detection telemetry for after the engagement. Track the forbidden list as a known-unknown in your coverage map — it is not “covered,” it is “untested.” This is one of the most under-used artefacts a SOC receives.

5.3 The Emergency Stop

Every engagement needs a way for the client to stop you in under five minutes, at any hour. Concretely:

• A phrase (HALT ENG-2291) that means “stop everything now, no questions, we will discuss later.”
• A channel that works out of hours — a phone number, not an email alias.
• A named person on your side who is reachable, with a documented backup.
• An agreed acknowledgement time (e.g. “the team will confirm cessation within 15 minutes”).
• A rule that resumption requires written client approval, not a verbal “ok you can carry on.”

And on your side: know how to actually stop. A nuclei run inside a tmux session on a jump box you cannot reach from your phone is not stoppable. Mature teams run long jobs under a supervisor that responds to a kill switch, and keep a documented “how to stop everything” runbook that a colleague can execute without you.

Part 6: The Paperwork Stack

New testers assume there is one document. There are typically five to seven, each doing a different job.

Document	Purpose	Typically signed by	When	If missing
NDA (mutual)	Protects both parties’ confidential information	Both, legal	Before scoping conversations	You cannot receive architecture docs
MSA (Master Services Agreement)	Governs the overall commercial relationship: liability caps, IP, insurance, governing law	Both, legal	Once, covering many engagements	Every engagement renegotiates liability
SOW (Statement of Work)	This specific engagement: deliverables, dates, price, team	Both, commercial	Per engagement	No agreed deliverable; payment disputes
Rules of Engagement	Operational constraints (Part 5)	Client technical owner + tester lead	Per engagement, before testing	Ambiguity resolved against you
Authorization Letter	Standalone, plain-language proof that testing is authorised	Client executive with authority	Per engagement	No portable proof of consent
Scope Appendix + ownership attestation	The asset list and the client’s warranty that they own it	Client asset owner	Per engagement, re-signed if changed	You inherit the risk of their inventory errors
Data Processing Agreement	Governs personal data touched during testing	Both, privacy/legal	Where personal data is in play	GDPR/DPDP exposure for both parties
Physical authorization (“get-out-of-jail letter”)	Carried on-person during physical engagements	Client executive + site owner	Physical engagements only	Detention by police is a genuine risk

6.1 The Authorization Letter, Written Out

This is the document a tester should be able to draft from memory. It is short by design — it exists to be understood by a police officer, a hosting provider’s abuse desk, or a judge, none of whom will read your 40-page MSA.

                          AUTHORIZATION FOR SECURITY TESTING
                                Reference: ENG-2291-AUTH-v3

Contoso Retail Holdings Ltd ("Contoso"), a company registered in England and Wales
(No. 09876543) with registered office at [address], hereby authorises:

    Northwind Security Ltd ("Tester"), company No. 12345678
    Named personnel: A. Rahman, P. Silva, M. Chen

to perform security testing, including active vulnerability scanning and controlled
exploitation, against the systems enumerated in Appendix A ("the Authorised Systems"),
during the period:

    06 April 2026, 09:00 Europe/London  to  17 April 2026, 18:00 Europe/London

Contoso represents and warrants that it owns, or holds the contractual right to
authorise security testing of, each system listed in Appendix A.

This authorisation is subject to the Rules of Engagement document ENG-2291-ROE-v3
and the Statement of Work dated 24 March 2026, and is limited to the Authorised
Systems and the period stated above. It may be revoked at any time by written notice
to the Tester's engagement lead.

Contoso confirms that testing performed within these bounds is performed with its
knowledge and consent and does not constitute unauthorised access to its systems.

Emergency contact (24h):  Security Operations, +44 20 7946 0000
Emergency stop phrase:    HALT ENG-2291

Signed: ______________________     Date: ______________
        J. Okafor
        Chief Information Security Officer
        Contoso Retail Holdings Ltd

Notes on why each clause is there:

• Named personnel. Authorization runs to specific humans. If you add a team member mid-engagement, amend the letter — do not assume the company name covers them.
• “including active vulnerability scanning and controlled exploitation.” Without this, a client can later argue they authorised a scan but not exploitation.
• The warranty clause. This is your primary protection when the client’s inventory is wrong.
• Explicit time bounds. Authorization that never expires is authorization no lawyer will sign.
• Revocation clause. Its presence signals that both parties understood consent is ongoing.
• The reference number. Everything — the ROE, the scope file, the traffic marker, the report — uses the same ID, so any artefact can be tied back to the authority for it.

Carry it. For remote work, keep a signed PDF accessible offline. For physical engagements, carry paper copies, and give one to the client’s security guards’ supervisor in advance.

Part 7: Cloud and Third-Party Authorization

Almost every modern engagement touches infrastructure the client does not own. The client’s signature authorises testing of their tenancy; the provider’s policy governs everything underneath it.

Provider	General posture on customer pentesting	Prohibited without separate approval	Practical note
AWS	Permitted for a defined list of customer-operated services without prior approval	Any DoS/DDoS simulation, testing of other tenants, testing AWS-operated infrastructure (e.g. hypervisor), some managed services	Simulated-event form required for DDoS-style tests; policy is service-scoped, so check the current service list
Microsoft Azure	Permitted under the unified Microsoft Cloud penetration testing rules of engagement	Testing other tenants, phishing Microsoft staff, DoS	Rules cover M365 and Azure together
Google Cloud	Permitted without notification, subject to the Acceptable Use Policy	Anything violating the AUP; other tenants	Google explicitly says no form is needed but AUP still applies
Cloudflare	Edge is Cloudflare’s; testing the origin through it is a customer matter	Testing Cloudflare’s own edge/WAF infrastructure	Test the origin directly where possible; scanning through the CDN mostly tests Cloudflare
Shared hosting (cPanel-class)	Usually prohibited outright	Effectively everything intrusive	Other tenants on the same host make it untestable
SaaS (Salesforce, Workday, Okta, etc.)	Vendor-specific; often requires written pre-approval or is prohibited	Testing the multi-tenant platform	Client owns data, not the system
Managed security appliances	The MSSP owns them	Testing the appliance itself	Add to explicit out-of-scope list

Provider policies change. Do not memorise the specifics from any table, including this one — check the provider’s current published testing policy at the time of scoping, save a dated copy in the engagement file, and reference it in the ROE. That saved copy is your evidence of the policy you relied on.

7.1 The Cloud Attribution Problem

Cloud makes ownership verification genuinely hard, and this is where scope validation earns its keep.

An IP in AWS’s range tells you nothing about which customer it belongs to. 203.0.113.45 in whois returns Amazon, not Contoso. So how do you prove an in-scope IP belongs to your client rather than to a stranger’s EC2 instance that happens to sit in the same /16?

Three techniques, in order of strength:

1. Client-side proof. Ask the client to place a unique token at a known path, or to add a DNS TXT record, or to show you the resource in their console. If they can put ENG-2291-abc123 at https://host/.well-known/pentest-token and you can read it, they control that host. This is the strongest, cheapest check and it is under-used.
2. Certificate transparency + control-plane correlation. A TLS certificate issued for the client’s domain to that IP is meaningful evidence, especially with a DNS record chain you have verified.
3. Passive attribution. Reverse DNS, ASN, historical DNS records. Weakest — treat as a hint, never as proof.

Technique 1 is the one to build a habit around: when in doubt, make the client prove control rather than asserting it. It converts an ownership question into a five-minute technical check.

Part 8: Bug Bounty and VDP — Unilateral Authorization

Bug bounty is legally different from consulting. There is no negotiated contract; there is a public offer with terms, and your authorization is whatever that offer grants. You are bound by every word of the program policy, and you had no opportunity to negotiate any of it.

flowchart TD
    A[Find a program] --> B[Read the FULL policy, not the summary]
    B --> C{Is there explicit<br/>safe harbour language?}
    C -->|No| D[Higher risk — the program can<br/>still pursue you legally]
    C -->|Yes| E{Does safe harbour cover<br/>third parties too?}
    E -->|No| F[Only the program owner<br/>has promised not to sue]
    E -->|Yes| G[Stronger position]
    D --> H[Enumerate in-scope assets<br/>from the policy ONLY]
    F --> H
    G --> H
    H --> I{Asset resolves into<br/>declared scope right now?}
    I -->|No| J[Do not test — report<br/>the scope discrepancy instead]
    I -->|Yes| K[Test using ONLY permitted techniques]
    K --> L{Found something?}
    L -->|Yes| M[Minimal proof. Stop.<br/>Do not pivot, do not dump data]
    M --> N[Report through the<br/>designated channel only]
    N --> O[Follow the program's<br/>disclosure timeline]
    O --> P{Program unresponsive?}
    P -->|Yes| Q[Escalate via platform mediation<br/>NOT via public disclosure first]
    P -->|No| R[Coordinate publication date]

8.1 Reading a Safe Harbour Clause

Safe harbour language varies enormously in strength. Learn to grade it.

Weak — a promise not to sue, conditional and vague:

“We will not pursue legal action against researchers who act in good faith.”

Problems: “good faith” is undefined and judged by them; there is no mention of criminal referral; it does not bind third parties; it can be withdrawn.

Moderate — the common template, materially better:

“If you make a good faith effort to comply with this policy during your security research, we will consider your research to be authorized, we will work with you to understand and resolve the issue quickly, and we will not recommend or pursue legal action related to your research.”

Better because it uses the magic words “we will consider your research to be authorized” — that is a grant of authorization, directly addressing the element of the offence, not merely a promise about remedies.

Strong — adds third-party and DMCA coverage:

“…we will consider your research authorized, will not initiate or support legal action against you, will waive any restrictions in our Terms of Service that would prohibit your research, and will take steps to make known that your activities were authorized if a third party initiates legal action against you. We also grant a limited exemption under DMCA § 1201 for research within this policy.”

The ToS waiver matters because a ToS breach is a separate contract claim that safe harbour otherwise leaves alive. The third-party assistance clause matters because your hosting provider or the police are not parties to the program’s promise.

Safe harbour element	What it protects against	How often present
“We consider your research authorized”	The core criminal element	Common in mature programs
“We will not pursue legal action”	Civil suit by the program owner	Very common
“We waive relevant ToS restrictions”	Breach-of-contract claim	Less common, valuable
DMCA § 1201 exemption	Anti-circumvention claim	Uncommon, matters for hardware/DRM
Third-party defence assistance	Claims by hosts, partners, other vendors	Rare, the strongest signal
Clear scope + technique list	Ambiguity about what was authorized	Should be universal, is not
Named disclosure timeline	Disputes over publication	Improving

disclose.io maintains standardised safe-harbour language that many programs adopt verbatim; recognising it saves reading time and tells you the program has thought about this properly.

8.2 The Ways Bounty Hunters Actually Get in Trouble

These are the recurring patterns, and none of them are exotic:

• Testing an asset that “looks like” it belongs to the target. contoso-cdn.example is not *.contoso.example. Subdomains found by a tool are not scope; the policy is scope.
• Escalating beyond minimal proof. Finding an IDOR and then iterating the ID a hundred thousand times to build a “impact demonstration” dataset. That is a data breach you caused.
• Automated scanning where the policy forbids it. Many programs ban automated scanners outright, and a nuclei run against a live production host is trivially detectable.
• Testing production sign-up flows at scale, creating thousands of accounts, sending real emails to real users, or triggering SMS charges.
• Going public after frustration. A program’s slow triage is aggravating; publishing before the agreed timeline converts a researcher into a defendant in a way nothing else does.
• Attempting to negotiate payment after finding a flaw in a program with no bounty, or with wording that reads as a demand. That crosses into extortion territory extremely fast — the DOJ policy’s “pretext” carve-out exists precisely for this.
• Testing an out-of-scope asset “just to check” and reporting it anyway. The report is evidence of the unauthorized access.

Bug bounty note, stated plainly: the winning behaviour is boring. Read the policy fully, screenshot the scope and the date, test only listed assets, prove minimally, report promptly through the designated channel, and never publish before the agreed date. Every high-earning hunter with a long career does exactly this.

Part 9: Hands-On Lab — Proving You Are Allowed to Test This

This is the practical core of the chapter. Before the first scan, an experienced tester independently verifies every asset in the scope. Here is that process end to end, with real tools, real flags and realistic output.

Lab objective: given a scope file listing domains and IP ranges, produce an evidence pack proving each asset is controlled by the client, and a validator that refuses to run tooling against anything unverified.

Lab environment: Kali Linux (or any Linux with the tools below). Everything here uses passive or minimally intrusive lookups against public registries — it is safe to run against the RFC 5737 documentation ranges used as examples, and you should substitute your own authorized targets.

9.1 Tooling From Zero

Four tools do most of the work. Install them first.

# Debian/Ubuntu/Kali
sudo apt update
sudo apt install -y whois dnsutils jq curl golang-go

# whois     — queries registry databases for domain and IP allocation records
# dnsutils  — provides dig, the canonical DNS query tool
# jq        — command-line JSON processor; we parse API responses with it
# curl      — HTTP client; used against the crt.sh certificate transparency API

whois is a client for a decades-old protocol (RFC 3912) that queries registry databases. It has two distinct uses that beginners conflate: querying a domain returns registrar and registrant data; querying an IP address returns the allocation record from a Regional Internet Registry (ARIN, RIPE, APNIC, LACNIC, AFRINIC). Those are entirely different databases with different meanings.

dig (Domain Information Groper) is the reference DNS client. Key flags:

Flag	Meaning	Why you want it here
+short	Print only the answer data	Scriptable output
+noall +answer	Suppress everything except the answer section	Readable but complete
@8.8.8.8	Query a specific resolver	Bypass a caching resolver that may be stale or hijacked
+trace	Walk delegation from the root	See which nameservers actually control the zone
-x <ip>	Reverse lookup (PTR)	Attribution hint for an IP
+dnssec	Request DNSSEC records	Confirms the answer chain is signed
TXT / NS / CAA	Record type	TXT for ownership tokens, NS for delegation, CAA for cert issuance policy

crt.sh is a public search interface over Certificate Transparency logs — the append-only public ledgers every trusted CA must log issued certificates to. It has a JSON endpoint, which makes it scriptable.

9.2 Step One — Domain Ownership

whois contoso-retail.example | grep -Ei 'registrant|org|admin|name server|creation|expiry|status'

Realistic output:

Registrant Organization:  Contoso Retail Holdings Ltd
Registrant Country:       GB
Admin Organization:       Contoso Retail Holdings Ltd
Name Server:              NS1.CONTOSO-DNS.EXAMPLE
Name Server:              NS2.CONTOSO-DNS.EXAMPLE
Creation Date:            2009-11-04T10:22:31Z
Registry Expiry Date:     2027-11-04T10:22:31Z
Domain Status:            clientTransferProhibited

Reading this like a professional:

• Registrant Organization matching the client’s legal name on the authorization letter is your primary positive signal. A mismatch is not automatically fatal — companies register domains through brand protection agencies like MarkMonitor or CSC — but it must be explained and the explanation recorded.
• Privacy redaction is now the norm, not the exception. Post-GDPR, most registrars return REDACTED FOR PRIVACY for registrant fields on many TLDs. When that happens, whois cannot prove ownership and you fall back to the token method in 9.5.
• Registry Expiry Date is a genuine finding in itself. A domain expiring in eleven days that is load-bearing for authentication is a risk worth reporting before you scan anything.
• Domain Status: clientTransferProhibited is a good sign — the registrar lock is on. Its absence is worth a note in the report (domain hijacking risk).

9.3 Step Two — IP Range Attribution

whois 203.0.113.20 | grep -Ei 'netname|orgname|organisation|country|cidr|inetnum|netrange|abuse-mailbox'

Realistic output for client-owned space:

NetRange:       203.0.113.0 - 203.0.113.63
CIDR:           203.0.113.0/26
NetName:        CONTOSO-DMZ-01
Organization:   Contoso Retail Holdings Ltd (CONTO-42)
Country:        GB
OrgAbuseEmail:  abuse@contoso-retail.example

That is a clean result: the CIDR matches the scope entry exactly, and the organisation matches the client. Contrast with a cloud-hosted asset:

NetRange:       52.94.0.0 - 52.95.255.255
CIDR:           52.94.0.0/15
NetName:        AMAZON-2011L
Organization:   Amazon Technologies Inc. (AT-88-Z)
Country:        US
OrgAbuseEmail:  abuse@amazonaws.com

This proves nothing about your client. It tells you the IP is in AWS. Millions of other customers share that allocation. This is precisely the cloud attribution problem from Part 7.1, and it is the moment you escalate to the token method.

For a quick ASN view across many IPs at once, Team Cymru’s whois service is the efficient tool:

# Bulk ASN lookup — one line per IP, no per-query rate pain
echo -e "begin\nverbose\n203.0.113.20\n198.51.100.14\n52.94.236.248\nend" \
  | nc whois.cymru.com 43

AS      | IP               | BGP Prefix     | CC | Registry | Allocated   | AS Name
64500   | 203.0.113.20     | 203.0.113.0/24 | GB | ripencc  | 2004-01-20  | CONTOSO-AS, GB
64501   | 198.51.100.14    | 198.51.100.0/24| GB | ripencc  | 2005-06-11  | CONTOSO-AS, GB
16509   | 52.94.236.248    | 52.94.236.0/22 | US | arin     | 2015-09-02  | AMAZON-02, US

Two client-owned prefixes under the client’s own ASN — strong evidence. One AWS prefix — no evidence at all. That distinction is the entire point of the exercise.

9.4 Step Three — Certificate Transparency

curl -s "https://crt.sh/?q=%25.contoso-retail.example&output=json" \
  | jq -r '.[] | "\(.not_before[0:10])  \(.issuer_name | split(",")[-1])  \(.name_value)"' \
  | sort -u | head -20

2025-08-14   O=Let's Encrypt   shop.contoso-retail.example
2025-08-14   O=Let's Encrypt   www.contoso-retail.example
2025-09-02   O=Let's Encrypt   api.contoso-retail.example
2026-01-11   O=Let's Encrypt   stage.contoso-retail.example
2026-01-11   O=Let's Encrypt   *.stage.contoso-retail.example
2026-02-20   O=DigiCert Inc    vpn.contoso-retail.example
2026-03-01   O=Let's Encrypt   internal-jenkins.contoso-retail.example

Two things happen here, and both matter.

As scope validation: certificates issued for the client’s domain confirm that whoever requested them demonstrated control of that domain to a CA. That is meaningful evidence of control.

As a scope-completeness check: internal-jenkins.contoso-retail.example appears in a public log but is not in the scope file. This is now a scoping conversation, not a target. The correct action is to send the client the list and ask: is this yours, should it be in scope, and — separately — are you aware your internal Jenkins hostname is publicly enumerable via CT logs? That last question is itself a finding, and one of the more valuable pieces of pre-engagement output you can deliver.

CTF and bounty relevance: CT log mining is the same technique used for subdomain discovery on bounty targets. The difference between research and trespass here is entirely about what you do with the list — enumerate freely from public logs, but only send packets to what the policy lists.

9.5 Step Four — The Ownership Token (the decisive check)

When registry data is redacted or the asset is cloud-hosted, ask the client to prove control. Two forms:

# Form A: HTTP path token
curl -s https://shop.contoso-retail.example/.well-known/pentest-token
# ENG-2291-8f3a1c9d4b

# Form B: DNS TXT token — works even when there is no web server
dig +short TXT _pentest-auth.contoso-retail.example
# "ENG-2291-8f3a1c9d4b"

Generate the token yourself, send it to the client, and require them to publish it. A token you generate cannot be guessed, so its presence proves administrative control at the moment you checked.

# Generate a token bound to the engagement
printf 'ENG-2291-%s\n' "$(openssl rand -hex 5)"
# ENG-2291-8f3a1c9d4b

Record the timestamp, the token, and the raw response in the evidence pack.

9.6 Step Five — Re-Resolution and the Automated Gate

Now automate all of it, so that no tool ever runs against an unverified target. This script is the deliverable of the lab.

#!/usr/bin/env python3
"""
scope_guard.py — refuse to run tooling against anything outside authorised scope.

Usage:
    python3 scope_guard.py --scope scope.yaml --targets targets.txt
    python3 scope_guard.py --scope scope.yaml --targets targets.txt --exec "nuclei -l {file}"

Exit codes:
    0  all targets verified in scope
    2  one or more targets failed validation (nothing is executed)
"""

import argparse
import ipaddress
import socket
import subprocess
import sys
import tempfile
from datetime import datetime, timezone

import yaml   # pip install pyyaml

def load_scope(path):
    with open(path) as fh:
        return yaml.safe_load(fh)

def window_is_open(scope):
    """Gate 4 from Part 1: authorisation must be currently valid."""
    start = datetime.fromisoformat(scope["engagement"]["window_start"])
    end = datetime.fromisoformat(scope["engagement"]["window_end"])
    now = datetime.now(timezone.utc)
    return start <= now <= end, start, end

def allowed_networks(scope):
    nets = []
    for key in ("ipv4", "ipv6"):
        for entry in scope.get("in_scope", {}).get(key, []) or []:
            nets.append(ipaddress.ip_network(entry, strict=False))
    return nets

def excluded_hosts(scope):
    return set(scope.get("out_of_scope", {}).get("explicit", []) or [])

def resolve(target):
    """Resolve a hostname to every address it currently answers with."""
    try:
        ipaddress.ip_address(target)
        return [target]
    except ValueError:
        pass
    try:
        infos = socket.getaddrinfo(target, None)
    except socket.gaierror as exc:
        return [f"UNRESOLVED:{exc.strerror}"]
    return sorted({info[4][0] for info in infos})

def validate(target, nets, excludes):
    if target in excludes:
        return False, f"{target}: explicitly excluded by scope"
    addrs = resolve(target)
    verdicts = []
    ok = True
    for addr in addrs:
        if addr.startswith("UNRESOLVED"):
            ok = False
            verdicts.append(f"{addr} — cannot verify, refusing")
            continue
        ip = ipaddress.ip_address(addr)
        inside = any(ip in net for net in nets)
        verdicts.append(f"{addr} {'IN SCOPE' if inside else 'OUT OF SCOPE'}")
        ok = ok and inside
    return ok, f"{target}: " + "; ".join(verdicts)

def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--scope", required=True)
    ap.add_argument("--targets", required=True)
    ap.add_argument("--exec", dest="command",
                    help="command to run if all targets pass; {file} is substituted")
    args = ap.parse_args()

    scope = load_scope(args.scope)
    open_now, start, end = window_is_open(scope)
    if not open_now:
        print(f"[ABORT] Outside authorised window ({start} .. {end}). "
              f"Now: {datetime.now(timezone.utc)}")
        sys.exit(2)

    nets = allowed_networks(scope)
    excludes = excluded_hosts(scope)
    targets = [ln.strip() for ln in open(args.targets) if ln.strip()
               and not ln.startswith("#")]

    failures = []
    verified = []
    for target in targets:
        ok, detail = validate(target, nets, excludes)
        print(("[PASS] " if ok else "[FAIL] ") + detail)
        (verified if ok else failures).append(target)

    print(f"\n{len(verified)} verified, {len(failures)} rejected "
          f"(engagement {scope['engagement']['id']})")

    if failures:
        print("[ABORT] Refusing to execute. Resolve scope issues first.")
        sys.exit(2)

    if args.command:
        with tempfile.NamedTemporaryFile("w", suffix=".txt", delete=False) as tf:
            tf.write("\n".join(verified) + "\n")
            path = tf.name
        cmd = args.command.replace("{file}", path)
        print(f"[EXEC] {cmd}")
        sys.exit(subprocess.call(cmd, shell=True))

if __name__ == "__main__":
    main()

Run it:

$ cat targets.txt
shop.contoso-retail.example
api.contoso-retail.example
198.51.100.14
payments.contoso-retail.example
old-cdn.contoso-retail.example

$ python3 scope_guard.py --scope scope.yaml --targets targets.txt
[PASS] shop.contoso-retail.example: 203.0.113.20 IN SCOPE
[PASS] api.contoso-retail.example: 203.0.113.21 IN SCOPE
[PASS] 198.51.100.14: 198.51.100.14 IN SCOPE
[FAIL] payments.contoso-retail.example: explicitly excluded by scope
[FAIL] old-cdn.contoso-retail.example: 104.18.32.77 OUT OF SCOPE

2 verified, 2 rejected (engagement ENG-2291)
[ABORT] Refusing to execute. Resolve scope issues first.

Look closely at the last failure. old-cdn.contoso-retail.example is a subdomain of the client’s own domain — it would have sailed through a naive *.contoso-retail.example wildcard. It resolves to 104.18.32.77, which is Cloudflare space, not the client’s. Scanning it would have meant attacking a CDN provider’s infrastructure under a wildcard the client had no authority to grant. That single line of output is the entire chapter, made operational.

Wire it into the workflow so it cannot be skipped:

# Wrap every tool invocation
python3 scope_guard.py --scope scope.yaml --targets targets.txt \
  --exec "nuclei -l {file} -H 'User-Agent: ENG-2291-PENTEST' -rate-limit 20"

python3 scope_guard.py --scope scope.yaml --targets targets.txt \
  --exec "nmap -iL {file} -sV --max-rate 200 -oA scans/eng2291-\$(date +%s)"

flowchart LR
    A[scope.yaml<br/>signed + versioned] --> B[scope_guard.py]
    C[targets.txt<br/>from recon] --> B
    B --> D{Window open?}
    D -->|No| X[ABORT]
    D -->|Yes| E{Re-resolve each host}
    E --> F{All addresses inside<br/>authorised CIDRs?}
    F -->|No| X
    F -->|Yes| G{Any explicit exclusion hit?}
    G -->|Yes| X
    G -->|No| H[Write verified target file]
    H --> I[Execute tool with<br/>rate limit + UA marker]
    I --> J[Log everything:<br/>timestamps, commands, output]

9.7 Lab Checkpoint

You should now be able to answer, for any asset handed to you:

1. Who does the registry say owns the domain, and does that match the authorization letter?
2. Which ASN and allocation does the IP belong to, and is it the client’s or a provider’s?
3. What certificates exist for this name, and do the CT logs reveal assets missing from scope?
4. Can the client demonstrate live control via a token you generated?
5. Does the name still resolve into authorized space right now, at execution time?
6. Is the engagement window currently open?

If any answer is “no” or “unknown,” the correct action is a conversation, not a scan.

Part 10: Data Handling, Evidence and Minimum Sufficient Proof

Once testing starts, the legal risk shifts from access to data. You are now handling someone else’s information, potentially including personal data of people who never heard of you.

10.1 The Minimum Sufficient Demonstration Principle

For every finding, ask: what is the smallest artefact that proves this to a skeptical engineer?

Vulnerability	Over-exploitation (wrong)	Minimum sufficient proof (right)
SQL injection	Dump the users table	SELECT @@version output, plus SELECT COUNT(*) FROM users and the column names from information_schema
IDOR	Iterate 50,000 IDs and save responses	Two requests: your own record, and one other record with the fields redacted in the report
SSRF	Pull IAM credentials and use them	Screenshot the metadata endpoint responding, with the credential body redacted; do not use the credentials unless the ROE says so
RCE	Install a reverse shell and persist	id, hostname, and a timestamped file write in /tmp that you then delete
Exposed S3 bucket	Download the bucket	aws s3 ls output showing object names and count
Password hash dump	Crack them all	Prove read access to the store; crack a small sample only if the ROE explicitly authorises password auditing
Stored XSS	Deploy a keylogger against real users	alert(document.domain) or a benign token beaconed to your own listener, targeting only your test account
Broken access control on admin panel	Change production settings	Screenshot the panel rendering with your low-privilege session, changing nothing

That table is arguably the most practically important one in the chapter. Over-exploitation is how competent testers create the incident they were hired to prevent.

10.2 Handling Data You Do Encounter

Data class	Rule	Storage	Retention
Credentials found (hashes, keys, tokens)	Report existence; do not reuse beyond ROE	Encrypted vault, engagement-scoped	Destroy at closure; attest in writing
Personal data (PII)	Redact in reports; never copy in bulk	Encrypted volume, no cloud sync	Destroy at closure
Payment / cardholder data	Do not capture at all. Stop and escalate	N/A	N/A — PCI scope contamination
Health / special-category data	Treat as PII with stricter handling; often a hard stop	Encrypted, access-logged	Destroy immediately
Screenshots	Redact before they enter the report	Encrypted engagement share	Per contract, typically 90 days
Full packet captures	Only if ROE permits; they contain everything	Encrypted, engagement-scoped	Destroy at closure
Tool output / logs	Retain — this is your audit trail	Encrypted, integrity-hashed	Per contract, often longer

Practical hygiene that costs nothing:

• Keep every engagement on a dedicated encrypted volume (LUKS, VeraCrypt, FileVault sparse bundle), mounted only while working, never on a synced cloud folder.
• Hash your evidence as you collect it, so its integrity is provable later:

  find ./evidence -type f -exec sha256sum {} \; | tee evidence/MANIFEST.sha256
  sha256sum -c evidence/MANIFEST.sha256   # verify at handover

• Log every command you run with a timestamp. script or a shell hook does this for free:

  script -f -c "bash" ~/eng-2291/logs/session-$(date -u +%Y%m%dT%H%M%SZ).log

  This log is what proves you stayed in scope. It has saved careers.
• Deliver the report over an encrypted channel — PGP, a client-controlled secure portal, or a password-protected archive with the passphrase over a separate channel. A pentest report is the single most attacker-valuable document a company owns; emailing it in plaintext is a self-inflicted breach.
• Issue a written destruction attestation at closure listing what was held and confirming secure deletion. Clients increasingly require it, and it closes your own liability.

Part 11: When Things Go Wrong

They will. The professional difference is not avoiding all incidents; it is handling them correctly in the first ten minutes.

flowchart TD
    A[Something unexpected happened] --> B{Which category?}
    B -->|Touched out-of-scope asset| C[STOP that activity immediately]
    B -->|Caused an outage| D[STOP everything. Call the emergency contact NOW]
    B -->|Found evidence of prior compromise| E[STOP. Preserve. Do not investigate further]
    B -->|Found illegal content| F[STOP. Do not copy, do not view further]
    B -->|Client asks for out-of-scope work| G[Do not proceed on a verbal request]

    C --> C1[Preserve logs of exactly what was sent and when]
    C1 --> C2[Notify client in writing within hours, not days]
    C2 --> C3[Delete any data obtained; attest to deletion]
    C3 --> C4[Root-cause it: how did the gate fail?]

    D --> D1[Do not try to fix it yourself]
    D1 --> D2[Hand over full command log immediately]
    D2 --> D3[Support their IR; write a factual timeline]

    E --> E1[This is now Incident Response, not a pentest]
    E1 --> E2[Notify client executive contact immediately]
    E2 --> E3[Do not alert the intruder by poking their tooling]
    E3 --> E4[Client decides: convert engagement or pause]

    F --> F1[Notify client legal + your own counsel immediately]
    F1 --> F2[Follow jurisdictional reporting duties exactly]

    G --> G1[Request a written scope amendment]
    G1 --> G2[Amend ROE + authorization letter, then proceed]

11.1 The Out-of-Scope Touch

You will eventually scan something you should not have. A typo, a stale DNS record, a wildcard that resolved somewhere new. The instinct is to say nothing, because nothing bad happened and disclosure is embarrassing.

Disclose it, promptly and in writing. Reasons, in order of force:

1. It is almost always in the contract as an obligation.
2. The client’s logs will show it. Being the one who reported it makes it a professional self-correction; being caught makes it a cover-up.
3. If the out-of-scope asset belongs to a third party, that party may complain, and your client needs to have known first.
4. It is the only way the root cause gets fixed.

Write it as facts, not apology: what was sent, to what, at what timestamp, what data was returned, what you have deleted, and what control you are adding so it cannot recur.

11.2 Discovering a Real, Prior Compromise

This is the highest-stakes scenario in the chapter, and it happens more often than most people expect — you scan a DMZ host and find a webshell that is not yours, with a modification date from four months ago.

The rules:

• Stop testing that host. Your activity is now contaminating an incident scene.
• Do not interact with the attacker’s tooling. Do not curl the webshell, do not run their binary, do not connect to their C2. You could alert them, trigger destruction, or be mistaken for them.
• Preserve what you already have — your logs, timestamps, the exact response that revealed it.
• Escalate immediately to the executive contact, not the engineer you have been working with day to day. This may be a reportable breach with regulatory clocks (GDPR’s 72-hour notification, sector rules) that only an executive can start.
• Expect the engagement to change shape. Either it pauses, or it converts to IR under a new contract. Do not simply continue as if nothing happened.
• Consider that the client may be a victim of an attack they must disclose — and that you must not disclose. Your NDA still binds you.

11.3 The Verbal Scope Expansion

A client engineer says, mid-call: “while you’re in there, can you also check the VPN concentrator?”

The answer is always some form of: “happy to — send me a one-line email confirming it is added to scope and I will start after that.” It is not bureaucracy. The engineer may not have authority (Part 3), the asset may be third-party managed, and if anything goes wrong, a verbal request evaporates. A two-line email that says “Adding vpn.contoso-retail.example (203.0.113.30) to ENG-2291 scope, effective immediately — J. Okafor, CISO” takes ninety seconds and is a genuine authorization artefact.

Part 12: Ethics Beyond Legality

Legality is the floor, not the ceiling. Plenty of things are legal and still wrong, and a career is built on the difference.

The grey zones that actually come up:

• The unresponsive vendor. You reported a critical flaw; ninety days passed; they never replied. Publishing pressures them to fix it and warns users — and also arms attackers against users who cannot patch. There is no universally right answer. The defensible path is documented, repeated, good-faith attempts through multiple channels, a clear pre-announced timeline, a coordinated route through a CERT/CSIRT or CNA, and withholding weaponised exploit details even when publishing the advisory.
• Findings the client wants softened. A client asks you to downgrade a Critical to a Medium because a Critical triggers a board report. Your name is on the document. Downgrading a severity you do not believe is professional dishonesty with real downstream consequences, and it is how consultancies lose credibility permanently. Negotiate the wording, never the facts.
• Scope that is deliberately designed to miss. Sometimes a scope excludes exactly where the problems are, so the report can be waved at an auditor. You can decline, or you can accept and state the limitation prominently in the executive summary. What you cannot do is let the report imply a coverage it never had.
• Exploit publication. Publishing a working exploit for a widely deployed, unpatched system does arm both defenders and attackers. Reasonable practitioners disagree; the mainstream norm is to publish after a patch exists and a reasonable deployment window has passed, and to withhold the most weaponisable components.
• Selling to brokers or offensive vendors. Legal in many jurisdictions. It also removes any control over who is targeted with your work. This is a values decision, and it deserves to be made deliberately rather than drifted into.
• Testing beyond consent “for the greater good.” The intuition that a serious flaw justifies unauthorized deeper testing is exactly the intuition the law does not share, and it is the single most common way researchers have been prosecuted.
• The client with a hostile use case. You are asked to test a system whose purpose you find objectionable. You are allowed to decline. Practitioners who never think about this until the day it arrives tend to make worse decisions than those who have.

A working ethical test. Before an ambiguous action, ask three questions: Would I be comfortable describing exactly this in the report? Would I be comfortable if the affected user could see it? Is there a less intrusive action that achieves the same legitimate goal? If the answer to the third is yes, do that instead — that is what minimum sufficient proof (Part 10.1) formalises.

Part 13: Disclosure Models and Timelines

Model	Who is told, and when	Typical timeline	Strengths	Risks
Private / non-disclosure	Vendor only; never public	Indefinite	No attacker benefit	Users never learn; no pressure to fix
Coordinated (CVD)	Vendor first, public after fix or deadline	90 days typical (Google Project Zero: 90 + 14 grace)	Balances pressure and safety	Requires a responsive vendor
Full disclosure	Public immediately	0 days	Maximum pressure; users can mitigate	Arms attackers against unpatched users
Coordinated through a CERT/CNA	National CERT or CNA coordinates	45–90 days typical	Works when the vendor is unresponsive or the flaw spans many vendors	Slower; coordination overhead
Bounty platform mediated	Platform triages and mediates	Program-defined	Structured; has an escalation path	Bound by program terms

13.1 The Practical CVD Workflow

sequenceDiagram
    participant R as Researcher
    participant V as Vendor
    participant C as CNA / CERT
    participant P as Public

    R->>V: Report via security.txt / PSIRT / bounty platform
    Note over R: Keep a timestamped record of every attempt
    V-->>R: Acknowledge (target: 5 business days)
    R->>V: Propose disclosure date (e.g. T+90)
    V->>V: Triage, reproduce, develop fix
    V-->>R: Reproduction confirmed + severity agreed
    R->>C: Request CVE assignment (via vendor CNA or MITRE)
    C-->>R: CVE-YYYY-NNNNN reserved
    V->>P: Patch released
    V-->>R: Fix confirmed, credit agreed
    R->>P: Advisory published on agreed date
    Note over R,V: If vendor goes silent: escalate to CERT,<br/>then publish on the pre-announced date

Two mechanics worth knowing concretely:

security.txt (RFC 9116) is the standardised way to find where to report. Always check it first:

curl -s https://example.com/.well-known/security.txt

Contact: mailto:security@example.com
Expires: 2027-01-01T00:00:00.000Z
Encryption: https://example.com/pgp-key.txt
Acknowledgments: https://example.com/hall-of-fame
Preferred-Languages: en
Policy: https://example.com/security-policy

CVE assignment goes through a CNA (CVE Numbering Authority). Large vendors are their own CNA; for everyone else, MITRE acts as CNA of last resort via its request form. A CVE is an identifier, not a severity — CVSS scoring is separate, and vendors and researchers frequently disagree on it.

Part 14: Detection & Defense Angle

Everything so far has been from the tester’s side. Flip it, because the defender’s job here is substantial and usually done badly.

14.1 Deconfliction: Telling Your Testers From Real Attackers

The core defensive problem during an engagement is attribution ambiguity. If the SOC cannot tell authorized testing from a real intrusion, one of two failures follows: they burn a week investigating their own pentest, or — far worse — they dismiss a genuine intrusion as “probably the testers.”

The second failure is a real and recurring pattern: an actual attacker operating during an announced test window, whose activity is written off as expected noise.

Controls that work, in order of value:

1. A deconfliction log, not an allow-list. Record the test’s source IPs, window and marker in the SIEM as context, not as a suppression rule. Alerts still fire; analysts see an enrichment field saying “matches ENG-2291 declared source.” They still triage, but with information.
2. A traffic marker enrichment rule. A SIEM rule that tags events containing the agreed User-Agent or source IP with engagement_id=ENG-2291.
3. Positive deconfliction, both directions. When the SOC sees something ambiguous, they call the test lead and ask “was this you at 14:32?” — and the tester answers from their command log within minutes. When the tester sees something that is not theirs, they call the SOC. This requires both sides to keep good logs; the script session log from Part 10.2 is what makes the tester’s half possible.
4. A rule that anything not confirmed as the test is treated as real. The default must be “unattributed until proven otherwise,” never “assume it is the pentest.”
5. Post-engagement reconciliation. Take the tester’s full activity log and replay it against your detections. Every action they took that produced no alert is a detection gap with a known ground truth — this is the single highest-value artefact of the entire engagement for a detection engineer, and most SOCs never ask for it.

flowchart TD
    A[Alert fires during test window] --> B{Source IP in<br/>deconfliction log?}
    B -->|No| C[Treat as REAL. Full IR.]
    B -->|Yes| D{Traffic marker present?}
    D -->|No| E[Suspicious: declared IP, undeclared marker]
    E --> F[Call test lead for confirmation]
    D -->|Yes| F
    F --> G{Tester confirms from<br/>their command log?}
    G -->|Yes, with matching timestamp| H[Tag as engagement activity<br/>Record as detection hit]
    G -->|No / cannot confirm| C
    H --> I[Post-engagement:<br/>compare tester log vs alerts]
    I --> J[Every unalerted action<br/>= confirmed detection gap]

14.2 Log Evidence a Defender Should Keep

Because testing generates the same telemetry as attacks, the defender’s evidence discipline mirrors the tester’s:

# Scope a Zeek/Suricata review to declared tester sources for reconciliation
zcat /var/log/zeek/conn*.log.gz \
  | zeek-cut -d ts id.orig_h id.resp_h id.resp_p proto service duration orig_bytes \
  | awk '$2=="192.0.2.44" || $2=="192.0.2.45"' \
  | head

# Find HTTP requests carrying the agreed marker
zcat /var/log/zeek/http*.log.gz \
  | zeek-cut -d ts id.orig_h host uri user_agent status_code \
  | grep 'ENG-2291-PENTEST' | wc -l

2026-04-08T02:11:03+0100  192.0.2.44  203.0.113.20  443  tcp  ssl   0.412  1204
2026-04-08T02:11:04+0100  192.0.2.44  203.0.113.21  443  tcp  ssl   0.388  1180
2026-04-08T02:11:09+0100  192.0.2.45  203.0.113.20   22  tcp  ssh   1.004   932
14877

If the count of marked requests is far below the tester’s own reported request count, you have a visibility gap — traffic reaching the app that your sensors never saw. That is a finding about your monitoring, produced for free by the test.

14.3 The Defender’s Version of Authorization

Defenders need their own authorization discipline, and it is routinely overlooked:

• Monitoring employees. Endpoint agents, DLP and email inspection process personal data. In many jurisdictions this requires notice, a lawful basis, works-council consultation, or all three.
• Threat hunting on employee endpoints. Reading a user’s browser history during a hunt has privacy implications; have a documented policy for what analysts may access and when.
• Active defence / hack-back. Scanning or accessing an attacker’s infrastructure is unauthorized access. The attacker’s illegality does not create authorization for you. In essentially every jurisdiction, hack-back is a crime.
• Honeypots and canary tokens. Generally fine on your own infrastructure. Collecting data on the people who touch them can still trigger privacy law.
• Sharing IOCs and samples. Malware samples can contain victim personal data; sharing them externally may need review.

Part 15: Final Revision — The Chapter in Compressed Form

The core principle. Nothing in a packet makes it legal. Authorization is the entire difference, and it is a property of paperwork, not technology.

The four gates. Authorization must (1) exist, (2) cover this specific action, (3) come from someone with authority to grant it, and (4) still be valid right now. Any single failure puts you outside the law. Gates 3 and 4 fail most often and most quietly.

The legal landscape. Statutes worldwide criminalise access without authorization or in excess of it. Van Buren narrowed the US “exceeds authorized access” theory to a gates-up-or-down test, and the DOJ’s 2022 policy directs federal prosecutors away from good-faith research — but neither is a research exemption, neither binds states, foreign prosecutors or civil plaintiffs, and both can change. A signed contract with the actual owner outweighs all of them.

Authority. Only the party with the legal right to control the asset can consent. Not the developer, not the friendly IT manager, not the SaaS customer. Demand a written ownership attestation, then verify it yourself anyway.

Scope. Write it as structured data, not prose. Enumerate CIDRs and hosts. Qualify every wildcard with a resolution constraint. Name forbidden activities explicitly with numbers, not adjectives. Re-resolve at execution time, because DNS changes between scoping and scanning.

Rules of Engagement. The operational contract: window with timezone, source IPs, traffic marker, rate limits, permitted and forbidden techniques, credential and data handling, escalation path, an emergency stop that works at 3 a.m., and deconfliction.

Paperwork. NDA, MSA, SOW, ROE, authorization letter, scope appendix with ownership warranty, DPA where personal data is involved, and a physical letter you carry on site. The authorization letter is short on purpose — it must be readable by someone who will never see the MSA.

Cloud and third parties. The client authorises their tenancy; the provider’s policy governs the infrastructure. Cloud IPs prove nothing about ownership — make the client prove control with a token you generated.

Bug bounty. A unilateral public offer. You are bound by every word of a policy you did not negotiate. Grade the safe harbour language; “we will consider your research authorized” is the phrase that matters. Test only listed assets, prove minimally, never publish early, never let a report read as a demand for payment.

Proof discipline. Minimum sufficient demonstration. SELECT @@version, not a table dump. Two IDOR requests, not fifty thousand. Over-exploitation is how good testers cause the breach they were hired to prevent.

Data. Encrypted engagement volume, hashed evidence manifest, full command logs, redacted reports, encrypted delivery, written destruction attestation. The command log is what proves you stayed in scope.

When it goes wrong. Stop, preserve, disclose in writing, quickly, factually. On discovering a prior compromise: stop, do not touch the attacker’s tooling, escalate to an executive, expect the engagement to change shape. Never accept a verbal scope expansion.

Ethics above law. Legality is the floor. Never soften a severity you believe in. Never justify unauthorized depth by the importance of the finding. Ask whether a less intrusive action proves the same point — it usually does.

Defence side. Log the test, do not allow-list it. Enrich, do not suppress. Treat anything unconfirmed as real. Reconcile the tester’s full activity log against your alerts afterwards — that comparison is the most valuable detection artefact any engagement produces.

Part 16: Cheat Sheet / Quick Reference

The pre-flight checklist — every engagement, no exceptions

[ ] NDA + MSA executed
[ ] SOW signed, deliverables and dates agreed
[ ] ROE signed by client technical owner
[ ] Authorization letter signed by an executive with authority
[ ] Scope appendix signed, with ownership warranty clause
[ ] DPA in place if personal data may be touched
[ ] Cloud/third-party testing policies checked and a dated copy saved
[ ] Every asset independently verified (whois / ASN / CT / token)
[ ] Every hostname re-resolves into authorised ranges
[ ] Test window, timezone and no-test hours confirmed
[ ] Source IPs declared; traffic marker agreed
[ ] Rate limits and thread caps agreed
[ ] Emergency contact + stop phrase confirmed and tested
[ ] Deconfliction contact briefed; SOC told to log, not allow-list
[ ] Encrypted evidence volume created; command logging on
[ ] Insurance in force and adequate

Scope validation commands

# Domain registrant
whois example.com | grep -Ei 'registrant|org|name server|expiry|status'

# IP allocation
whois 203.0.113.20 | grep -Ei 'netrange|cidr|netname|orgname|country|abuse'

# Bulk ASN attribution
echo -e "begin\nverbose\n203.0.113.20\n198.51.100.14\nend" | nc whois.cymru.com 43

# Certificate transparency (also a scope-completeness check)
curl -s "https://crt.sh/?q=%25.example.com&output=json" | jq -r '.[].name_value' | sort -u

# Live resolution at execution time
dig +short shop.example.com
dig +short shop.example.com @1.1.1.1     # second opinion
dig -x 203.0.113.20 +short               # reverse hint

# Ownership token
curl -s https://host/.well-known/pentest-token
dig +short TXT _pentest-auth.example.com

# Where to report a vulnerability
curl -s https://example.com/.well-known/security.txt

Evidence hygiene

script -f -c bash ~/eng/logs/session-$(date -u +%Y%m%dT%H%M%SZ).log
find ./evidence -type f -exec sha256sum {} \; | tee evidence/MANIFEST.sha256
sha256sum -c evidence/MANIFEST.sha256
gpg --encrypt --recipient client-security@example.com report.pdf

Marked, rate-limited tool invocations

nmap -iL verified.txt -sV --max-rate 200 -oA scans/eng-$(date +%s)
ffuf -w wordlist.txt -u https://host/FUZZ -rate 20 -H "User-Agent: ENG-2291-PENTEST"
nuclei -l verified.txt -rate-limit 20 -H "User-Agent: ENG-2291-PENTEST"
sqlmap -r req.txt --threads 1 --delay 1 --level 2 --risk 1   # never default threads on prod

The severity-of-mistake ladder — what to do first, by scenario

Situation	First action	Within one hour
Scanned an out-of-scope host	Stop that activity	Written notice to client with timestamps
Caused an outage	Stop everything	Call emergency contact; hand over command log
Found a prior compromise	Stop touching the host	Escalate to executive contact
Found illegal content	Stop; copy nothing	Contact client legal and your own counsel
Client verbally expands scope	Do not proceed	Request written amendment
Engagement window expired	Stop all tooling	Request written extension before resuming
Credentials found and cracked	Do not reuse beyond ROE	Confirm handling rules in writing

Phrases to recognise in safe harbour language

Phrase	What it grants
“we will consider your research authorized”	Addresses the criminal element directly — strongest
“we will not pursue legal action”	Civil forbearance from the program owner only
“we waive restrictions in our Terms of Service”	Removes the breach-of-contract theory
“we will make known that your activities were authorized”	Help if a third party comes after you
“limited exemption under DMCA §1201”	Anti-circumvention cover
“good faith” with no definition	Weak — they judge it, after the fact

Memory hooks

• Consent is not in the packet. — It is in the paperwork, or it does not exist.
• Four gates: exists, covers, authorised grantor, still valid. — All four, every time.
• DNS is not ownership. — Re-resolve at execution; qualify every wildcard.
• Version string, not table dump. — Minimum sufficient proof.
• Log it, don’t allow-list it. — The defender’s rule for test traffic.
• Verbal scope is no scope. — Ninety seconds for an email is always worth it.

Part 17: Practice Labs & Resources

Train the specific skills in this chapter — this material is practised through documents and OSINT, not exploits, so the labs look different from other chapters.

Scope validation and attribution (extends Part 9):

• Pick three companies that run public bug bounty programs on HackerOne or Bugcrowd. For each, read the policy in full and build a scope.yaml in the Part 4.1 format purely from the published policy. Then run the Part 9 validation chain — whois, Team Cymru ASN lookup, crt.sh — against the listed assets and record which are client-owned versus provider-hosted. Send no packets to the targets themselves; registry and CT lookups only. Compare your derived scope against the policy and note every ambiguity you found.
• Run scope_guard.py against a scope file whose CIDRs you deliberately mis-specify, and confirm it refuses to execute. Then extend it: add CT-log cross-checking so it warns about hosts in the logs that are missing from scope.
• Use crt.sh and Censys/Shodan search (read-only) on a domain you own to see how much of your own attack surface is publicly enumerable without touching it.

Policy and paperwork reading:

• Read disclose.io’s standardised safe-harbour terms, then grade five real bug bounty policies against the Part 8.1 table. Write down which of the six elements each program has.
• Read the current published cloud testing policies for AWS, Azure and Google Cloud end to end. Write a one-page summary of what each permits without prior approval — this is a document you will reuse constantly.
• Read a real penetration test report template (the PTES and OSSTMM communities publish examples, and several consultancies publish sanitised samples) and identify where scope, ROE and limitations are disclosed.
• Read RFC 9116 (security.txt) and publish a valid one for a domain you control.

Methodology standards worth knowing by name:

• PTES (Penetration Testing Execution Standard) — the pre-engagement section is essentially this chapter in standards form.
• OWASP Web Security Testing Guide — its scoping and reporting chapters.
• NIST SP 800-115, Technical Guide to Information Security Testing and Assessment — the rules of engagement guidance is the most citable reference for a client who wants an authority.
• OSSTMM — heavier, but its “rules of engagement” section is rigorous.
• CREST and TIBER-EU / DORA TLPT frameworks — how regulated financial-sector testing is authorised, useful if you go anywhere near banking.

Disclosure practice:

• Find a vulnerability in an open-source project you use (start with dependency-scanning your own projects), and take it through the full coordinated disclosure workflow in Part 13.1 — including finding the right contact via security.txt or SECURITY.md, agreeing a timeline, and requesting a CVE if warranted. Doing this once end to end teaches more than any amount of reading.
• Read ten disclosed HackerOne reports and note, for each, how much proof the researcher provided. Calibrate your own sense of “minimum sufficient” against what triagers actually accepted.

Legal grounding:

• Read the EFF’s security research legal resources and Van Buren v. United States (the majority opinion is short and readable).
• Read the DOJ 2022 CFAA charging policy memo directly — it is a few pages.
• Find and read your own jurisdiction’s computer crime statute. If you are in India, that is IT Act ss. 43, 65, 66; in the UK, the Computer Misuse Act 1990. Knowing the actual text of the law that governs you is a thirty-minute investment with a very long payoff.

Practice questions to self-test:

1. A client’s CISO signs an authorization letter listing *.contoso.example. During recon you find support.contoso.example resolving to a Zendesk-owned IP. Using the four gates from Part 1 and the authority table in Part 3, explain precisely which gate fails, and write the exact email you would send the client.
2. You are mid-engagement when a finding requires you to pivot from an in-scope web server to a database host that is not listed, in order to demonstrate impact. Justify your decision using the minimum sufficient proof table in Part 10.1, and state what evidence you would deliver instead of the pivot.
3. A bug bounty policy says only “we will not pursue legal action against researchers acting in good faith.” Using Part 8.1, name three specific legal exposures that language leaves open, and one sentence you would want added to close each.
4. During a test window, the SOC sees a Kerberoasting attempt from an IP that is not on the declared source list, but arriving three minutes after a confirmed tester action. Using the Part 14.1 decision flow, state the correct next action and explain why the timing correlation is not sufficient attribution.
5. Your scope file lists 203.0.113.0/26. Ten days into the engagement, shop.contoso-retail.example begins resolving to 104.18.32.77. Explain what has probably happened, what scope_guard.py does about it, and why the same failure would have been invisible if you had resolved the hostname once at scoping time and cached the result.