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, and credit card numbers are not currently detected by the default configuration - see #7 for tracking status.

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 john@example.com

Result:

🛡️ Privacy Guard blocked this prompt

Found 2 sensitive item(s):
  - API_KEY: sk-proj-abc123xyz...
  - EMAIL: john@example.com...

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

Please remove or anonymize sensitive data before proceeding.

Configuration

Create a .privacy-guard.json file (searched upward from your current working directory, so a repo-root or home-directory config both work) to override the defaults. See .privacy-guard.example.json for a starter file.

Option	Type	Default	Status
enabled	boolean	true	✅ Implemented. Set to false to disable the plugin entirely without uninstalling it.
disabledRules	string[]	[]	✅ Implemented. Rule IDs to skip - see the built-in id fields in src/scanner/detectors.ts or the name fields in data/regex_list_1.json for external rules.
externalRulesJsonPath	string	./data/regex_list_1.json	✅ Implemented. Path (relative to the config file's directory) to the external regex dataset.
externalRulesMode	"coding-only" | "all"	"coding-only"	✅ Implemented. "coding-only" filters the external dataset down to rules whose name/description mentions a coding-secret keyword (key, token, secret, password, private key, etc.); "all" loads every external rule.
strictMode	boolean	false	⚠️ Accepted in config but not yet enforced by the scanner (#6).
allowedDomains	string[]	[]	⚠️ Accepted in config but not yet enforced by the scanner (#6).
redactionStyle	"placeholder" | "mask" | "remove"	"placeholder"	⚠️ Accepted in config but not yet enforced by the scanner (#6).
autoMaskOnHighRisk	boolean	true	⚠️ Accepted in config but not yet enforced by the scanner (#6).

Example:

{
  "enabled": true,
  "disabledRules": [],
  "externalRulesJsonPath": "./data/regex_list_1.json",
  "externalRulesMode": "coding-only"
}

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, updates CHANGELOG.md, runs build/test, creates commit+tag, and optionally pushes/publishes.

See CONTRIBUTING.md for how to add a detection rule and the dist/ rebuild requirement, and 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

Debug logging is off by default. To enable it, set PRIVACY_GUARD_DEBUG=1 in your environment before starting Claude Code, then check the log:

cat "${XDG_CACHE_HOME:-$HOME/.cache}/claude-code-privacy-guard/debug.log"

The log only contains execution metadata (working directory, Node version, exit codes) - it never contains matched secret or PII values.

Contributing

Contributions welcome! See CONTRIBUTING.md for dev setup, how to add a detection rule, and the release process.

License

MIT © Datum Brain