security-audit-methodology

Security Audit Methodology

Authorization and safety boundary

Before any assessment, confirm the target, scope, permitted techniques, data-handling rules, and escalation contact. Do not probe systems, access accounts, exploit findings, or alter production state without explicit authorization. Record findings as evidence for the responsible owner; this skill does not certify compliance or replace qualified security review.

Security is not a checklist — it's a posture. This methodology covers systematic evaluation of code, architecture, dependencies, and operational practices for security weaknesses.

The Security Engineer's Domain

You own	You don't own
Threat modeling — STRIDE, attack trees, trust boundaries	General code review — that's the qa-methodology
Vulnerability assessment — classification, severity, reproduction	Performance analysis — that's the systematic-debugging
Security architecture review — authn/authz, data flow, secrets management	Operational reliability — that's SRE
Dependency analysis — supply chain, known vulnerabilities, license risk	Compliance certification — that's legal
Security testing guidance — fuzzing, SAST/DAST integration	Incident response execution — that's SRE/on-call

Reference Files

Reference	When to load
references/threat-modeling.md	Evaluating a system's attack surface — STRIDE per component, trust boundaries, data flow analysis
references/vulnerability-classification.md	Assessing a finding — CVSS scoring, CWE mapping, severity triage, exploitability assessment
references/security-architecture-dependency-audit.md	Reviewing authentication (OAuth 2.0, OIDC, SAML, mTLS), authorization (RBAC/ABAC/ReBAC), session management, secrets management, and dependency/supply chain security (SBOM, CVE matching, license analysis, SLSA framework)

Core Principles

Trust nothing, verify everything — Every input, every boundary, every assumption is a potential attack surface. Default deny, explicit allow.

Defense in depth — No single control is sufficient. Authentication without rate limiting, encryption without key management, input validation without output encoding — each is a vulnerability waiting to chain.

Least privilege — Every component, every user, every process should have exactly the permissions it needs and no more. Over-privilege is the most common security debt.

Understand the attacker's perspective — The question isn't "can this be exploited?" It's "how would an attacker think about this system?" Model their incentives, constraints, and capabilities.

Fix the class, not the instance — One SQL injection means you need parameterized queries everywhere, not just at that one endpoint. A single XSS means review the entire rendering pipeline.

Portability

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