Security Audit Skill: A Complete Tutorial for Turning Claude Code into an AI Security Auditor, from Code Scanning to a Full Vulnerability Report

A scan returns a list of suspicious code paths, but no clear proof of which ones are real vulnerabilities.

Fastest answer: Security Audit Skill can guide Claude Code through a repeatable, scoped review, evidence checks, and report drafting. Use it as an assistant, not as an automated security certification: results depend on the repository context, permitted tools, and human verification.

This guide is for developers standardizing code review with Claude Code, security engineers preparing findings for review, and technical leads evaluating AI-assisted audit workflows. It focuses on authorized repositories and a practical path from scope definition to a report that another person can verify.

Start with the right division of work

A Skill provides reusable instructions and workflow guidance. It does not independently prove that code is secure, and it does not turn an unsupported claim into a verified finding. Claude Code can inspect files and follow instructions, while configured scanning tools can provide additional signals within their own detection limits. A reviewer must decide whether the evidence demonstrates a vulnerability and whether the proposed impact is credible.

Approach	What it contributes	Main limitation	Best fit
Manual review alone	Context-sensitive reasoning about code, architecture, and business rules	Can be slow and inconsistent when the same review steps recur	High-impact logic and final validation
Static analysis alone	Repeatable checks for patterns covered by the configured rules	Results depend on rules, language support, configuration, and code visibility	Baseline checks and repeatable detection
Claude Code with a Security Audit Skill	A structured sequence for examining scope, evidence, and report quality	The model can miss issues or infer behavior that the code does not establish	Assisted review with a human reviewer

The practical goal is not to ask Claude Code to “find every vulnerability.” It is to make the review process more disciplined: define what is in scope, gather evidence, ask focused follow-up questions, and make uncertainty visible. That is particularly useful when a team needs consistent review notes across repositories or wants to turn scattered scanner output into a report that an engineer can reproduce.

The official Skills documentation describes the supported Skill format and loading conventions. The permissions documentation explains that tool use is governed by permission rules. Those are separate concerns: a Skill can request a tool-assisted check, but instructions alone should not be treated as authorization to run it.

Define an authorized audit boundary

Before scanning, write down which repository and revision may be examined, which directories matter, and which actions are allowed. “Review this project” is too vague for a dependable audit. A monorepo might contain generated output, vendored dependencies, test fixtures, infrastructure files, and several applications with different threat models. Without boundaries, the review can spend time on irrelevant material or fail to notice that an important component was excluded.

A clear scope note can look like this:

Authorized target: the current checkout of the team-owned sample API.
In scope: src/auth/, src/routes/, and configuration read by those modules.
Focus: authentication, authorization, input handling, and secret exposure.
Out of scope: deployment, production systems, external endpoints, and load testing.
Allowed actions: read repository files and run the preconfigured local checks.
Do not: modify files, contact external services, print secret values, or expand scope.

This is an illustrative template, not a substitute for the repository owner’s approval. Replace the sample paths with real, authorized paths, and do not include credentials or live secret values in the prompt. If the audit requires a command that changes files, accesses a network, or reads sensitive data, that action needs separate approval and a permission review.

The scope should include enough project context to interpret code. Note the application’s entry points, trust boundaries, authentication model, sensitive data, and the intended role of the module under review. If the project has an established security policy or a known set of unsupported checks, include that information too. A scanner result detached from architecture may look serious while being unreachable in the actual application; a model examining one function may miss that another layer enforces authorization.

Frameworks can help define review categories without implying complete coverage. The OWASP Top 10 2021 overview groups common web application risks into ten categories; it is a prioritization resource, not a promise that checking those categories finds every defect. The CWE weakness and vulnerability FAQ also helps distinguish a weakness in code from a demonstrated vulnerability in a particular context. Use those distinctions in the scope and report rather than treating a category label as proof of exploitability.

Build the Skill around an evidence-first sequence

Claude Code Skills use a SKILL.md file, and the official format specifies the name and description fields in the frontmatter. The Skills guide documents the directory and invocation conventions; check it when setting up the Skill because a misplaced file or invalid metadata can prevent the intended instructions from being available. Do not assume a Skill is active merely because its file exists.

A minimal instruction structure could be:

---
name: security-audit
description: Review authorized repository code for security concerns and produce evidence-based findings.
---

# Security audit workflow

## Scope
- Confirm the authorized repository, revision, directories, and exclusions.
- Stop and ask for clarification if the target or allowed actions are unclear.

## Review
- Read relevant project documentation and identify entry points and trust boundaries.
- Inspect in-scope code for the stated risk areas.
- Use only configured and permitted local analysis tools when appropriate.
- Do not modify files, contact external systems, or expose secret values.

## Evidence
- For each candidate, record the file, symbol or line range, relevant code, and reasoning.
- Trace input to the sensitive operation and identify any controls in between.
- Separate confirmed findings, pending verification, and rejected candidates.

## Report
- Include impact, confidence, remediation, and verification status.
- Do not claim exploitability or severity without supporting evidence.

The sequence matters. Starting with an unbounded “scan everything” instruction encourages broad, shallow output. Requiring Claude Code to establish scope first gives it a chance to stop when the task is ambiguous. Requiring evidence before severity discourages confident-sounding conclusions based only on a pattern match.

The Skill should also state what to do when evidence is missing. For example, if a reported path depends on runtime configuration that is not present in the checkout, the output should say that the behavior remains unverified. If a tool is unavailable or its output cannot be interpreted, the report should name the gap instead of implying that the check passed. This keeps “not checked” distinct from “checked and found safe.”

Permission rules need to be configured and reviewed independently of the Skill. The Claude Code security guidance and settings documentation describe security and permission-related controls. Use the narrowest practical access for the task; do not give an audit agent unrestricted authority just to make a workflow convenient. A read-only review is a sound default unless a specific, approved check needs more access.

Run a bounded scan and verify each candidate

Use a repository that the team owns or has explicit permission to audit. Before starting, confirm that the checkout is the intended revision and that local analysis tools are configured. The following workflow is designed to gather evidence without turning a review into an unapproved test against live systems.

Step one: provide the target and limits. State the repository, branch or revision, in-scope paths, risk focus, exclusions, and allowed actions. Ask Claude Code to restate the scope and list any ambiguity before reviewing code. Correct the scope before proceeding if it includes the wrong service, unclear ownership, or files that contain data the agent should not inspect.

Step two: supply relevant context. Point to project documentation, architectural notes, security conventions, and the entry points connected to the requested review. Do not paste secret values. If a configuration file contains credentials, provide a redacted version or describe the relevant setting without exposing its value.

Step three: request a structured inspection. Have the Skill direct Claude Code to identify potentially relevant code paths and explain why each one deserves review. It should name the source of input, the operation that could be sensitive, and any validation or authorization checks found along the way. A claim such as “this endpoint may be vulnerable” is not enough to make a finding.

Step four: run only approved local checks. When a configured static analysis tool is available and permitted, use its output as a separate evidence source. Record which check ran and what it reported. Tool output does not establish reachability or impact by itself, and a clean result does not prove the absence of defects outside the tool’s coverage.

Step five: trace and challenge each candidate. Open the cited code and verify that the file and location exist in the audited revision. Follow the relevant data flow, check the conditions under which the path executes, and look for controls that change the conclusion. Ask Claude Code to identify what evidence would disprove its own finding. This is useful for exposing assumptions about user input, authorization, or runtime configuration.

Step six: classify the result honestly. Use a small project-defined status vocabulary, such as confirmed, pending verification, and rejected. “Confirmed” should mean that a reviewer can reproduce the relevant behavior from code and supporting evidence. “Pending” means a meaningful question remains, such as a missing runtime setting or an uninspected authorization layer. “Rejected” should include the reason the suspected issue does not apply.

A finding can be a weakness without being an exploitable vulnerability in the deployed application. The distinction described in the CWE guidance is a reminder to avoid collapsing code patterns, weaknesses, and context-specific security impact into one label. Severity should follow the demonstrated impact and realistic preconditions, not the confidence of the prose or the presence of a scanner warning.

Turn findings into a reviewable vulnerability report

A useful report lets another engineer locate the evidence and independently assess the conclusion. It should preserve the reasoning chain, not just the final severity label. For each candidate, record the vulnerability type or weakness category, affected file and code location, relevant evidence, data flow, impact rationale, remediation, and verification state. Include uncertainty and assumptions where the evidence does not cover runtime behavior or deployment configuration.

A raw scan note might say:

Possible injection in request handler. High severity. Fix input.

That is not yet a defensible report. It omits the code location, the source of the value, whether a sensitive operation receives it, and what evidence supports the severity. A better draft would use a structure such as:

Title: Untrusted request value reaches a query construction path
Status: Pending verification
Affected location: src/routes/example-handler.ext, relevant handler function
Evidence: The request parameter is passed to the query-building helper at the cited call site.
Control review: No validation or parameterization was identified in the inspected path.
Impact rationale: Impact depends on whether the helper treats the value as executable query syntax.
Verification needed: Inspect helper implementation and confirm behavior in the application context.
Suggested action: Use a parameterized query or an approved validation strategy if the data flow is confirmed.

The sample is deliberately marked pending. It does not claim that exploitation is possible without verifying what the helper does. Once that behavior and the relevant execution path are established, a reviewer can revise the status and impact statement. If the helper safely parameterizes the value, the candidate may be rejected with that evidence recorded.

A report should separate observation from interpretation. “The parameter is passed to this helper” is an observation; “an attacker can execute arbitrary queries” is an impact claim that requires more evidence. The NIST Secure Software Development Framework organizes secure development practices into four practice groups, including practices concerned with reviewing and addressing defects. It supports treating remediation and follow-up as part of a development process, not as optional text appended to a scan result.

For severity, use the organization’s established classification method and explain the reasoning. Do not invent a numeric score when the required inputs are unavailable. A report can still be useful with a clear impact description, preconditions, affected component, and a status such as “awaiting runtime verification.” If a team uses a formal scoring system, the Skill should ask for its required evidence and leave the value unassigned when those inputs are missing.

Review the boundaries before accepting the report

Use this checklist before treating an AI-assisted audit as complete:

• [ ] Confirm the repository owner authorized the target, revision, and requested actions.
• [ ] Check that the Skill’s in-scope paths and exclusions match the approved task.
• [ ] Verify that prompts and tool output did not expose secret values or unnecessary sensitive data.
• [ ] Confirm that every reported file and code location exists in the audited revision.
• [ ] Trace each high-impact claim through the relevant code and control flow.
• [ ] Record which configured checks ran, which did not run, and why.
• [ ] Keep confirmed findings separate from pending questions and rejected candidates.
• [ ] Check that severity reflects evidence and stated assumptions.
• [ ] Make remediation specific enough for an engineer to implement and review.
• [ ] Re-run relevant checks or inspect the changed code after remediation.
• [ ] Escalate unclear authorization, sensitive-data exposure, access-control failures, or material impact claims to a qualified security reviewer.

This review is especially important when the finding concerns access control, business logic, secret handling, or a path whose behavior depends on configuration outside the repository. Static checks may not see runtime conditions, and a language model may infer a control that is absent—or overlook one implemented in another layer. The Claude Code security documentation should inform the environment’s security setup, while the team remains responsible for deciding whether a particular audit has sufficient access and safeguards.

Independent review triggers

Escalate rather than close the issue when the report proposes a high-impact conclusion but cannot show a complete data path, when the key behavior depends on unavailable runtime configuration, or when the proposed fix changes authorization or sensitive-data handling. Escalation is also appropriate if an approved tool reports a serious issue that the code review cannot reproduce, or if the scan’s scope excluded a component required to establish impact. In those cases, the report should preserve the candidate and state the specific evidence needed for resolution.

FAQ

How should a Security Audit Skill be configured?

Start with an authorized target, explicit in-scope paths, exclusions, language or component context, and named risk areas. Then require Claude Code to explain candidate findings with code evidence and to use only configured, permitted tools. Include a stop condition for unclear scope and a rule that missing runtime or architectural context must be reported as uncertainty, not silently filled in.

Can Claude Code produce a vulnerability report from scan results?

It can draft one, provided the Skill requires a consistent structure: affected location, evidence, relevant data flow, impact rationale, remediation, and verification status. A reviewer should inspect the cited code and supporting tool output before accepting the draft. A plausible explanation is not proof; keep a finding pending when reachability, controls, or runtime behavior remain unverified.

How should scan findings be verified and classified?

Check that the cited code exists in the audited revision, trace the value to the sensitive operation, and inspect any validation, authorization, or parameterization along the path. Use confirmed only when the evidence supports the behavior and impact. Use pending when a material question remains, and reject a candidate only after recording why the suspected condition does not apply.

Which parts still need a human reviewer?

A human should verify authorization, scope, high-impact code paths, severity assumptions, and whether remediation fits the application. Reviewers should also examine possible secret exposure, business logic, access control, and checks that available tools cannot cover. Claude Code can organize evidence and draft a report, but a qualified person must own the security conclusion and any decision to accept risk.

Choose an environment that fits the audit

For an isolated, short review, a developer’s local checkout may be enough, especially when the permitted checks are lightweight and the repository can remain on that machine. A managed remote development environment may be more suitable when a team needs a separate workspace or wants to run approved analysis away from a developer’s everyday machine. Neither option removes the need for repository authorization, least-privilege access, or careful handling of scan output.

A remote environment also has trade-offs: access must be managed, project data is processed outside the local workstation, and the team must verify that its required tools and controls are available before using it. A long-running, high-load audit workflow may be better served by infrastructure the organization directly operates. For temporary remote development or an isolated trial, the relevant question is whether the environment matches the audit’s access and data-handling requirements—not whether it promises automatic security.

Teams evaluating a cloud Mac can review Zutcloud’s Mac mini rental options and its service help center for current service details. Those pages should be checked against the project’s needs before moving code or credentials into any remote workspace. Before running the Skill, use the checklist above in an authorized repository, keep the first pass narrow, and escalate findings whose evidence or impact cannot be independently confirmed.