AgentShield

AI Agent Detection & Response (AADR) — real-time security monitoring with Sigma rules and LLM-powered triage.

What is AgentShield?

AgentShield is a Go security engine that monitors AI agent tool calls in real-time. It evaluates each call against Sigma security rules and optionally routes suspicious events through LLM triage for context-aware verdicts. It runs as a single binary with no external runtime dependencies.

Architecture

Single Go binary (agentshield) containing:

• HTTP server (Chi router, 127.0.0.1:8433 by default)
• Sigma rule engine (forked sigmalite in pkg/sigma/)
• SQLite alert/feedback store
• LLM triage (OpenAI or Anthropic provider, optional)
• Bearer token authentication (constant-time comparison)
• Per-IP rate limiting (~100 req/min, burst 10)

One systemd user service: agentshield-engine.service (Linux) or one launchd agent: ai.agentshield.engine (macOS).

Installation

Quick Install

./install.sh

The installer:

1. Detects platform (linux/darwin) and architecture (amd64/arm64)
2. Downloads binary from GitHub releases (falls back to go install)
3. Creates ~/.agentshield/ directory (rules, config, database)
4. Clones sigma-ai rules from agentshield-ai/sigma-ai
5. Generates a 64-character auth token
6. Writes ~/.agentshield/config.yaml
7. Creates a systemd user service (Linux) or launchd agent (macOS)
8. Patches OpenClaw plugin configuration via openclaw config patch
9. Starts the service and runs a health check

Manual Installation

# Build from source
go build ./cmd/agentshield/

# Create directory structure
mkdir -p ~/.agentshield/rules

# Clone rules
git clone --depth 1 https://github.com/agentshield-ai/sigma-ai.git ~/.agentshield/rules

# Generate auth token
openssl rand -hex 32

# Create config.yaml (see Configuration section)
# Start the engine
~/.agentshield/agentshield-engine serve --config ~/.agentshield/config.yaml

Configuration

Config file: ~/.agentshield/config.yaml

server:
  addr: "127.0.0.1"
  port: 8433

auth:
  token: "your-64-char-token-here"

rules:
  dir: "~/.agentshield/rules"
  hot_reload: true

store:
  sqlite_path: "~/.agentshield/agentshield.db"
  retention_days: 90
  cleanup_interval_hours: 24

evaluation_mode: "enforce"   # enforce | audit | shadow

log_level: "info"

# triage:
#   enabled: true
#   provider: "openai"        # openai | anthropic
#   model: "gpt-4o-mini"
#   api_key: "sk-..."
#   max_tokens: 500
#   timeout_sec: 10
#   health_check_mode: "full"  # full | connectivity

Environment Variable Overrides

Authentication

A 32+ character token is mandatory. Without it, the server refuses to start. The installer generates a 64-character hex token automatically.

# Generate manually
openssl rand -hex 32

# Or via Python
python3 -c "import secrets; print(secrets.token_hex(32))"

Evaluation Modes

• enforce: Blocks tool calls matching rules. Use in production.
• audit: Logs alerts without blocking. Default for testing.
• shadow: Silent monitoring. No user-visible alerts.

CLI Commands

# Start the server
agentshield serve --config ~/.agentshield/config.yaml [--daemon] [--verbose]

# Check server status (queries /api/v1/health)
agentshield status [--verbose]

# List recent alerts
agentshield alerts [-l LIMIT] [-s SEVERITY] [--since RFC3339] [-r RULE]

# List loaded rules
agentshield rules list

# Reload rules (sends SIGHUP to running server)
agentshield rules reload

# Analyze rule performance using feedback data
agentshield refine [rule-name] [--apply] [--threshold FP_RATE]

# Show version
agentshield version

Service Management

Linux (systemd user service):

systemctl --user status agentshield-engine
systemctl --user start agentshield-engine
systemctl --user stop agentshield-engine
systemctl --user restart agentshield-engine
journalctl --user -u agentshield-engine -f

macOS (launchd):

launchctl load ~/Library/LaunchAgents/ai.agentshield.engine.plist
launchctl unload ~/Library/LaunchAgents/ai.agentshield.engine.plist
tail -f ~/.agentshield/engine.log

API Endpoints

All endpoints are under /api/v1/. Authentication via Authorization: Bearer <token> header.

Server Limits

• Max request body: 1 MB
• Max field value: 10 KB
• Max fields per request: 100
• Rate limit: ~100 req/min per IP, burst 10
• Request timeout: 30 seconds

LLM Triage

Optional. When enabled, the engine sends suspicious events to an LLM for context-aware analysis.

Supported providers: openai, anthropic.

triage:
  enabled: true
  provider: "openai"
  model: "gpt-4o-mini"
  api_key: "sk-..."
  max_tokens: 500
  timeout_sec: 10
  health_check_mode: "full"   # "full" runs a model call; "connectivity" just checks /v1/models

Triage returns a verdict (block, allow, investigate), confidence (0-1), and reasoning. In the OpenClaw plugin, a high-confidence allow (>0.8) from triage overrides rule-based alerts.

Sigma Rules

Rules are stored in ~/.agentshield/rules/. The engine loads all .yml/.yaml files from this directory.

Rule Format

Standard Sigma format adapted for agent tool monitoring:

title: Suspicious File Access
id: file-access-monitor
description: Monitor for access to sensitive system files
logsource:
  category: agent-tool
detection:
  selection:
    tool: file_operation
    path|contains:
      - '/etc/passwd'
      - '/etc/shadow'
      - '.ssh/'
  condition: selection
level: medium

Managing Rules

• Hot reload is enabled by default (rules.hot_reload: true)
• Manual reload: agentshield rules reload (sends SIGHUP)
• List loaded rules: agentshield rules list
• Rules repository: agentshield-ai/sigma-ai

OpenClaw Integration

The plugin registers as agentshield in OpenClaw's plugin system. The installer patches OpenClaw config automatically:

{
  "plugins": {
    "entries": {
      "agentshield": {
        "enabled": true,
        "config": {
          "enabled": true,
          "endpoint": "http://127.0.0.1:8433/api/v1/evaluate",
          "auth_token": "<generated-token>",
          "timeout_ms": 200,
          "timeout_policy": "block"
        }
      }
    }
  }
}

Plugin hooks registered:

• before_tool_call (priority -100): Synchronous evaluation with timeout
• after_tool_call: Fire-and-forget audit report
• session_start, session_end, before_agent_start, agent_end: Lifecycle events

See the plugin README for full plugin documentation.

Troubleshooting

Engine Won't Start

# Check logs
journalctl --user -u agentshield-engine -n 50

# Run with verbose output
agentshield serve --config ~/.agentshield/config.yaml --verbose

# Test health endpoint
curl -s -H "Authorization: Bearer YOUR_TOKEN" http://127.0.0.1:8433/api/v1/health

Common Issues

• Auth token too short: Must be 32+ characters. Regenerate with openssl rand -hex 32.
• Port conflict: Check netstat -an | grep 8433. Change server.port in config.
• Rules not loading: Verify rules.dir path exists and contains .yml files.
• Triage timeouts: Increase triage.timeout_sec or switch to health_check_mode: "connectivity".

Testing the Engine Directly

curl -X POST http://127.0.0.1:8433/api/v1/evaluate \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "event_id": "test-001",
    "tool_name": "exec",
    "command": "ls -la",
    "params": {"command": "ls -la"},
    "fields": {"tool": "exec", "command": "ls -la"}
  }'

File Locations

Uninstallation

cd plugins/openclaw/skill
./uninstall.sh

This stops the service, removes ~/.agentshield/, reverts OpenClaw plugin config, and cleans up PATH references.

License

Apache 2.0