Claude Code Privacy Guard

🛡️ Prevent secrets and PII from being accidentally shared with Claude Code.

A privacy-first plugin for Claude Code that scans prompts for sensitive data and blocks them before they reach the AI.

Features

• ✅ Blocks prompts containing sensitive data before they're sent to Claude
• ✅ Detects PII, secrets, API keys, tokens, and sensitive information
• ✅ Works locally - all scanning happens on your machine
• ✅ Zero configuration - works out of the box
• ✅ Detailed reporting - shows exactly what was detected

Installation

# Add the marketplace (if not already added)
/plugin marketplace add datumbrain/claude-code-privacy-guard

# Install the plugin
/plugin install claude-code-privacy-guard

⚠️ Important: Restart Required

After installing the plugin, you must restart your Claude Code session for it to take effect. This is because hooks are registered at session startup - Claude Code doesn't dynamically load new hooks mid-session.

Simply close and reopen Claude Code, or start a new session.

Once restarted, the plugin will automatically scan all prompts before they reach Claude.

What Gets Detected

✅ Secrets

• OpenAI API keys (sk-..., sk-proj-...)
• AWS credentials
• GitHub tokens
• Stripe keys
• JWT tokens
• Bearer tokens
• SSH private keys
• Generic API key patterns

✅ Personal Information (PII)

• Email addresses
• Phone numbers
• Social Security Numbers
• Credit card numbers

How It Works

1. You type a prompt in Claude Code
2. Privacy Guard intercepts it via a UserPromptSubmit hook
3. Scans for sensitive data using regex patterns
4. Blocks the prompt if sensitive data is found
5. Shows you exactly what was detected

Blocking relies on the UserPromptSubmit hook JSON protocol: the hook prints {"decision": "block", "reason": "..."} to stdout and exits with code 0. (Exit code 0 is required for the JSON decision to be honored - a non-zero exit is treated as a non-blocking hook error, and the prompt would go through anyway.)

Example

Input:

My API key is sk-proj-abc123xyz and email is [email protected]

Result:

🛡️ Privacy Guard blocked this prompt

Found 2 sensitive item(s):
  - API_KEY: sk-proj-abc123xyz...
  - EMAIL: [email protected]...

Risk Score: 100/100
Secrets: 1 | PII: 1

Please remove or anonymize sensitive data before proceeding.

Development

# Clone the repository
git clone https://github.com/datumbrain/claude-code-privacy-guard.git
cd claude-code-privacy-guard

# Install dependencies
npm install

# Build
npm run build

# Test the scanner directly
echo "test sk-proj-abc123" | node scripts/prompt-guard.js

Release:

make release

This runs an interactive flow that asks for version bump, confirms release actions, then runs build/test, creates commit+tag, and optionally pushes/publishes.

External regex dataset:

• Converted rules are stored at data/regex_list_1.json
• By default, external rules are loaded in coding-only mode (focus on keys/tokens/secrets/password/private key patterns)
• Set .privacy-guard.json to control behavior:

{
  "externalRulesJsonPath": "./data/regex_list_1.json",
  "externalRulesMode": "coding-only"
}

See docs/ for detailed architecture and integration guides.

Privacy & Security

• ✅ All scanning happens locally on your machine
• ✅ No data is sent to external services
• ✅ No telemetry or tracking
• ✅ Open source and fully auditable
• ✅ The plugin only blocks - it doesn't store or log your sensitive data

Why Block Instead of Redact?

Claude Code's hook system doesn't support transforming prompts - only blocking or adding context. Blocking ensures sensitive data never reaches the AI, which is the safest approach.

Debugging

Check the debug log if you encounter issues:

cat /tmp/claude-code-privacy-guard.log

Contributing

Contributions welcome! Please feel free to submit a Pull Request.

License

MIT © Datum Brain