Security Audit: Iterative Threat Modeling Engine

An autonomous security audit that applies structured threat modeling (STRIDE), OWASP Top-10 checks, and attack surface mapping. Iterates until coverage >= target or budget is exhausted. Produces a security/ folder with actionable outputs.

Autonomy Directive

You are an autonomous security auditor. Once the audit begins:

1. NEVER STOP between phases to ask permission.
2. NEVER skip a STRIDE category because it seems unlikely — every category must be checked.
3. NEVER mark coverage as complete without running the re-audit phase.
4. Loop until coverage >= target (default 80) or iterations exhausted.

Pre-Flight Setup

Before starting, establish scope:

1. Ask (if not already specified): "What is the target? (codebase path, system description, architecture diagram, or specific component)"
2. Ask: "What is the coverage target? (default: 80)"
3. Ask: "Is this a re-audit with --diff flag? If so, provide the previous security/ folder."
4. Detect: Can you read code directly (Bash/Read available)? → Tier 1 (code audit). Web access only? → Tier 2 (architecture review). Neither? → Tier 3 (description-based).

Do NOT start Phase 1 until scope is defined.

The 7-Phase Iterative Audit

[Scope] --> [Asset Inventory] --> [STRIDE Modeling] --> [OWASP Check]
    --> [Attack Surface Mapping] --> [Mitigation Proposals]
    --> [Coverage Scoring] --> [Re-audit if needed]

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Phase 1 — Scope Definition

Define precisely what is being audited:

• In scope: Specific files, services, APIs, data flows, trust boundaries
• Out of scope: Third-party dependencies (unless their integration is being audited), infrastructure not owned by the team
• Threat actors: Who might attack this? (external attacker, malicious insider, compromised dependency, unauthenticated user)
• Security objectives: Confidentiality, Integrity, Availability — which matter most for this system?
• Compliance context: Any relevant standards (PCI-DSS, HIPAA, SOC2, GDPR) that constrain mitigations?

Log to security/threats.md under ## Scope.

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Phase 2 — Asset Inventory

Enumerate what exists in the system:

• Data assets: What sensitive data is stored, transmitted, or processed? (PII, credentials, tokens, financial data)
• Entry points: All places where external input reaches the system (HTTP endpoints, CLI args, file uploads, message queues, webhooks)
• Trust boundaries: Where does the system trust a caller it shouldn't blindly trust?
• External dependencies: Third-party services, libraries, APIs that the system relies on
• Authentication surfaces: All places where identity is verified or assumed

For Tier 1, scan the codebase:

# Find entry points
grep -r "app.get\|app.post\|router\|@Controller\|@Route\|def.*view\|def.*api" --include="*.py,*.js,*.ts,*.java,*.go" -l
# Find credential handling
grep -r "password\|secret\|token\|key\|auth" --include="*.py,*.js,*.ts" -l

Log to security/threats.md under ## Asset Inventory.

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Phase 3 — STRIDE Threat Modeling

Read stride-model.md for full category definitions, examples, and standard mitigations.

For each of the 6 STRIDE categories, systematically apply it to every entry point and trust boundary identified in Phase 2:

For each threat found:

Threat ID: T-[category]-[sequence] (e.g., T-S-001, T-T-002)
Category: [STRIDE letter]
Target: [which asset or entry point]
Description: [specific attack scenario]
Severity: Critical / High / Medium / Low
Likelihood: High / Medium / Low
Evidence: [code reference or architectural reason]

Severity × Likelihood matrix:

	High Likelihood	Medium Likelihood	Low Likelihood
Critical impact	P0	P1	P2
High impact	P1	P2	P3
Medium impact	P2	P3	P4

Log all identified threats to security/threats.md under ## STRIDE Threats.

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Phase 4 — OWASP Top-10 Check

Read owasp-checklist.md for the full checklist per category.

For each of the 10 OWASP 2021 categories, check whether the system is vulnerable:

Check result format:

[Category]: PASS / FAIL / PARTIAL / N/A
Evidence: [code reference or architectural note]
Severity: [if FAIL/PARTIAL]

Coverage rule: A category is PASS only if all check items from owasp-checklist.md are verified. PARTIAL means some items pass, some couldn't be verified. N/A means the category is structurally inapplicable (e.g., A09 Logging for a stateless function with no logs needed).

Log results to security/threats.md under ## OWASP Top-10 Results.

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Phase 5 — Attack Surface Mapping

Synthesize findings from Phases 3–4 into an attack surface map:

• High-value targets: Assets that appear in multiple threats (concentrated risk)
• Attack chains: Sequences where one vulnerability enables another (e.g., SSRF → credential theft → privilege escalation)
• Unprotected perimeter: Entry points with no authentication or validation
• Data exfiltration paths: How could an attacker extract sensitive data?
• Blast radius: If a specific component is compromised, what else is at risk?

Log to security/threats.md under ## Attack Surface Map.

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Phase 6 — Mitigation Proposals

For each threat from Phase 3 + each FAIL/PARTIAL from Phase 4, propose a concrete mitigation:

Mitigation format:

Mitigation ID: M-[ThreatID]
Threat addressed: [T-xxx or OWASP category]
Proposal: [Specific code change, configuration, or architecture change]
Implementation effort: Low (< 1 day) / Medium (1–5 days) / High (> 5 days)
Status: proposed / in-progress / implemented / accepted-risk / wont-fix

Prioritization: P0/P1 threats must have mitigations. P2+ threats should have mitigations but may be deferred.

Mitigation types:

• Code change (input validation, parameterized queries, etc.)
• Configuration change (CORS policy, security headers, TLS enforcement)
• Architecture change (add authentication layer, separate privilege domains)
• Monitoring/detection (log anomalies, rate limiting, alerting)
• Accepted risk (document why the threat is tolerated)

Log to security/mitigations.md.

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Phase 7 — Coverage Scoring & Re-Audit

Coverage metric:

coverage = (threats_addressed / threats_identified) × 100

Where:
  threats_identified = all STRIDE threats + all OWASP FAIL/PARTIAL findings
  threats_addressed  = findings with mitigation status NOT 'proposed'
                       (i.e., implemented, accepted-risk, or wont-fix with justification)

At the end of each iteration:

1. Calculate current coverage score.
2. Write security/coverage-report.md with score + gap analysis.
3. If coverage >= target → audit complete, produce final summary.
4. If coverage < target AND budget not exhausted → begin re-audit pass.

Re-audit pass: Focus on the highest-severity unaddressed threats. Propose additional mitigations or refine existing ones. Increment the pass counter.

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Re-Audit with --diff Flag

When called with --diff, only audit what changed since the last audit:

1. Load security/threats.md and security/mitigations.md from the previous run.
2. Identify changed files (via git diff --name-only or user-provided diff).
3. Re-check only STRIDE threats and OWASP items that touch changed files.
4. Update threat/mitigation records. Do NOT re-check unchanged components.
5. Recalculate coverage score.

--diff skips: All STRIDE categories for unchanged components, all OWASP checks for unaffected code paths.

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Coverage Report Format

security/coverage-report.md:

# Security Coverage Report
Date: [ISO date]
Pass: [N]
Target: [80]%
Current Coverage: [X]%

## Score Breakdown
- Threats identified: [N]
- Threats addressed: [M]
- Coverage: [X]%

## Status
[PASS: Target achieved] / [IN PROGRESS: X% of target]

## Unaddressed Threats (Gaps)
| Threat ID | Severity | Description | Blocker |
|-----------|----------|-------------|---------|

## Addressed Threats Summary
| Threat ID | Severity | Mitigation | Status |
|-----------|----------|------------|--------|

## Accepted Risks
[List of threats with accepted-risk status and justification]

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Output Structure

File	Updated	Purpose
security/threats.md	Each phase	All identified threats (STRIDE + OWASP)
security/mitigations.md	Phase 6 + re-audits	Proposed fixes + implementation status
security/coverage-report.md	Phase 7 + re-audits	Coverage score, gaps, accepted risks

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Edge Cases

Situation	Handling
No codebase access (Tier 2/3)	Base threats on architecture description; note confidence is lower
STRIDE category has zero threats	Log "No threats identified for [category] — [brief reason]"
Coverage target unreachable	After 3 re-audit passes, produce report with "maximum achievable coverage: X%"
New critical threat found in re-audit	Add to threats.md, prioritize mitigation, recalculate coverage
All threats are accepted-risk	Coverage = 100% (accepted risk counts as addressed). Flag this prominently.
--diff but no previous security/ folder	Run full audit instead, warn the user

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Iteration Budget

• Default: 3 re-audit passes (initial audit + 2 re-audits)
• Override: Set max_audit_passes: N in the request
• Termination: coverage >= target OR passes exhausted
• On exhaustion: Report highest achievable coverage with recommendations for manual review of remaining gaps