Guard Scanner

---
name: guard-scanner
description: >
  Security scanner for AI agent skills. Use BEFORE installing or running any new skill
  from ClawHub or external sources. Detects prompt injection, credential theft,
  exfiltration, identity hijacking, sandbox violations, code complexity, config impact,
  and 17 more threat categories.
  Includes a Runtime Guard hook that blocks dangerous tool calls in real-time.
homepage: https://github.com/koatora20/guard-scanner
metadata:
  clawdbot:
    emoji: "🛡️"
    category: security
    requires:
      bins:
        - node
      env: []
    files: ["src/*", "hooks/*"]
    primaryEnv: null
    tags:
      - security
      - scanner
      - threat-detection
      - supply-chain
      - prompt-injection
      - sarif
---

# guard-scanner 🛡️

Static + runtime security scanner for AI agent skills.
**186+ threat patterns** across **20 categories** — zero dependencies.

## When To Use This Skill

- **Before installing a new skill** from ClawHub or any external source
- **After updating skills** to check for newly introduced threats
- **Periodically** to audit your installed skills
- **In CI/CD** to gate skill deployments

## Quick Start

### 1. Static Scan (Immediate)

Scan all installed skills:

```bash
node skills/guard-scanner/src/cli.js ~/.openclaw/workspace/skills/ --verbose --self-exclude
```

Scan a specific skill:

```bash
node skills/guard-scanner/src/cli.js /path/to/new-skill/ --strict --verbose
```

### 2. Runtime Guard (OpenClaw) — ⚠️ warn-only currently

> **Note:** OpenClaw `InternalHookEvent` does not yet expose cancel/veto. Runtime hook detections are warning + audit log until [Issue #18677](https://github.com/openclaw/openclaw/issues/18677) is adopted.

```bash
openclaw hooks install skills/guard-scanner/hooks/guard-scanner
openclaw hooks enable guard-scanner
openclaw hooks list
```

### 3. Recommended order

```bash
# Pre-install / pre-update gate first
node skills/guard-scanner/src/cli.js ~/.openclaw/workspace/skills/ --verbose --self-exclude --html

# Then keep runtime monitoring enabled
openclaw hooks install skills/guard-scanner/hooks/guard-scanner
openclaw hooks enable guard-scanner
```

## Runtime Guard Modes

Set in `openclaw.json` → `hooks.internal.entries.guard-scanner.mode`:

| Mode | Intended Behavior | Current Status |
|------|-------------------|----------------|
| `monitor` | Log all, never block | ✅ Fully working |
| `enforce` (default) | Block CRITICAL threats | ⚠️ Warn only (cancel API pending) |
| `strict` | Block HIGH + CRITICAL | ⚠️ Warn only (cancel API pending) |

> **Note:** OpenClaw's `InternalHookEvent` does not yet expose a `cancel`/`veto` mechanism. All detections are currently logged and warned via `event.messages`, but tool execution cannot be blocked. Blocking will be enabled when the cancel API is added.

## Threat Categories

| # | Category | What It Detects |
|---|----------|----------------|
| 1 | Prompt Injection | Hidden instructions, invisible Unicode, homoglyphs |
| 2 | Malicious Code | eval(), child_process, reverse shells |
| 3 | Suspicious Downloads | curl\|bash, executable downloads |
| 4 | Credential Handling | .env reads, SSH key access |
| 5 | Secret Detection | Hardcoded API keys and tokens |
| 6 | Exfiltration | webhook.site, DNS tunneling |
| 7 | Unverifiable Deps | Remote dynamic imports |
| 8 | Financial Access | Crypto wallets, payment APIs |
| 9 | Obfuscation | Base64→eval, String.fromCharCode |
| 10 | Prerequisites Fraud | Fake download instructions |
| 11 | Leaky Skills | Secret leaks through LLM context |
| 12 | Memory Poisoning | Agent memory modification |
| 13 | Prompt Worm | Self-replicating instructions |
| 14 | Persistence | Cron jobs, startup execution |
| 15 | CVE Patterns | Known agent vulnerabilities |
| 16 | MCP Security | Tool/schema poisoning, SSRF |
| 17 | Identity Hijacking | SOUL.md/IDENTITY.md tampering |
| 18 | Sandbox Validation | Dangerous binaries, broad file scope, sensitive env |
| 19 | Code Complexity | Excessive file length, deep nesting, eval density |
| 20 | Config Impact | openclaw.json writes, exec approval bypass |

## External Endpoints

| URL | Data Sent | Purpose |
|-----|-----------|---------|
| *(none)* | *(none)* | guard-scanner makes **zero** network requests. All scanning is local. |

## Security & Privacy

- **No network access**: guard-scanner never connects to external servers
- **Read-only scanning**: Only reads files, never modifies scanned directories
- **No telemetry**: No usage data, analytics, or crash reports are collected
- **Local reports only**: Output files (JSON/SARIF/HTML) are written to the scan directory
- **No environment variable access**: Does not read or process any secrets or API keys
- **Runtime Guard audit log**: Detections logged locally to `~/.openclaw/guard-scanner/audit.jsonl`

## Model Invocation Note

guard-scanner **does not invoke any LLM or AI model**. All detection is performed
through static pattern matching, regex analysis, Shannon entropy calculation,
and data flow analysis — entirely deterministic, no model calls.

## Trust Statement

guard-scanner was created by Guava 🍈 & Dee after experiencing a real 3-day
identity hijack incident in February 2026. A malicious skill silently replaced
an AI agent's SOUL.md personality file, and no existing tool could detect it.

- **Open source**: Full source code available at https://github.com/koatora20/guard-scanner
- **Zero dependencies**: Nothing to audit, no transitive risks
- **Test suite**: 55 tests across 13 sections, 100% pass rate
- **Taxonomy**: Based on Snyk ToxicSkills (Feb 2026), OWASP MCP Top 10, and original research
- **Complementary to VirusTotal**: Detects prompt injection and LLM-specific attacks
  that VirusTotal's signature-based scanning cannot catch

## Output Formats

```bash
# Terminal (default)
node src/cli.js ./skills/ --verbose

# JSON report
node src/cli.js ./skills/ --json

# SARIF 2.1.0 (for CI/CD)
node src/cli.js ./skills/ --sarif

# HTML dashboard
node src/cli.js ./skills/ --html
```

## License

MIT — [LICENSE](LICENSE)