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Mac Mini Security Hardening

Last Updated: January 30, 2026
Author: Josh Fletcher
Purpose: Harden Mac Mini AI agent boxes to minimize prompt injection attack surface

Overview​

When running AI agents with shell access on a Mac Mini, you need to isolate sensitive credentials from the agent while maintaining necessary functionality. This guide walks through hardening a Mac Mini running OpenClaw/Claude/Codex agents.

Threat Model​

Primary Risk: Prompt injection attacks where malicious input tricks the AI agent into:

  • Extracting credentials from keychain
  • Authenticating to services on your behalf
  • Exfiltrating sensitive data

Key Principle: Remove high-value credentials from the agent box. The agent only needs what it actively uses.

Hardening Steps​

1. Contact Migration (Google → iCloud)​

Goal: Get contacts on the Mac Mini for name resolution (iMessage, Reminders) without storing Google OAuth credentials.

Steps:

  1. Go to contacts.google.com
  2. Select all contacts → Export → Choose vCard format
  3. Download the .vcf file
  4. On the Mac Mini:
    • Open Contacts.app
    • File → Import → Select the .vcf file
    • Contacts will import to your iCloud account
  5. On your MacBook/iPhone:
    • System Settings → Internet Accounts → Google
    • Disable Contacts sync (keep Mail/Calendar if needed)
  6. Run the duplicate finder:
    • Contacts.app → Card menu → Look for Duplicates → Merge

Result: iCloud is now your single source of truth. No Google account on the Mac Mini.

2. iCloud Keychain Isolation​

Goal: Prevent personal passwords/passkeys from syncing to the agent box.

Steps:

  1. On the Mac Mini:
    • System Settings → Apple ID → iCloud
    • Find Passwords and Keychain
    • Toggle "Sync this Mac" to OFF
  2. Confirm in the Passwords app — you'll see a "Turn on iCloud Keychain" prompt

Result: Mac Mini has an isolated local keychain. MacBook/iPhone keep their synced credentials.

3. Keychain Cleanup​

Goal: Remove all passwords/passkeys from the Mac Mini except what's needed (Wi-Fi).

⚠️ CRITICAL: Order Matters

  • Do this AFTER disabling iCloud Keychain sync
  • If you delete before disabling sync, it deletes from all devices!

Steps:

  1. Open Passwords app on Mac Mini
  2. Select all non-Wi-Fi entries (Cmd+Click to multi-select)
  3. Delete them
  4. Go to Recently Deleted category
  5. Select all → Delete permanently

Result: Mac Mini keychain only contains Wi-Fi passwords.

4. Keychain Audit​

Check for remaining credentials:

# Search for Google credentials
security find-internet-password -s "google.com" 2>&1
security find-generic-password -l "Google" 2>&1
security dump-keychain 2>&1 | grep -i google

# Search for Gmail
security find-internet-password -s "gmail.com" 2>&1
security dump-keychain 2>&1 | grep -i gmail

Expected findings:

  • Apple Assistant (Siri) may have your Gmail address stored for email reading
  • This is metadata, not a credential — safe to leave

5. Contact Cleanup (Optional)​

Clean up years of accumulated random contacts:

Recommended approach:

  1. Export current contacts as backup
  2. Review categories:
    • Family - keep
    • Close friends - keep
    • Work contacts you actively use - keep
    • Services/businesses - keep only active ones
    • Old/random contacts - delete
  3. Use Contacts.app to delete in batches

Pro tip: Delete from the Mac Mini AFTER import. Changes sync to iCloud, so all your devices get the cleaned-up list.

Security Boundaries​

High-Value (Keep OFF Mac Mini)​

  • Gmail/Google account (master key for password resets)
  • Banking/financial credentials
  • Personal passwords/passkeys
  • Work VPN/SSH keys

Low-Value (Acceptable on Mac Mini)​

  • Claude/OpenAI web OAuth (chat access only, no billing control)
  • Wi-Fi passwords (required for functionality)
  • Apple Assistant metadata (no auth capability)

Current State Verification​

After hardening, your Mac Mini should have:

  • ✅ No Google account in System Settings → Internet Accounts
  • ✅ iCloud Keychain sync disabled
  • ✅ Passwords app shows only Wi-Fi entries (plus "Turn on iCloud Keychain" prompt)
  • ✅ Contacts syncing via iCloud only
  • ✅ OAuth tokens for Claude/OpenAI only (low-impact if compromised)

Your MacBook/iPhone should still have:

  • ✅ Google account active (for Mail/Calendar, Contacts disabled)
  • ✅ iCloud Keychain enabled with all passwords/passkeys
  • ✅ Same clean contact list

Future Enhancements​

Optional: 2FA on AI Service Accounts​

Enable 2FA on Claude and OpenAI accounts for an additional security layer:

  • Anthropic (Claude): Supports TOTP (Authy, Google Authenticator)
  • OpenAI: Supports TOTP or SMS

Even if OAuth tokens are compromised, attackers can't change settings without 2FA.

Optional: Hardware Security Keys​

For maximum security on your main devices (MacBook/iPhone):

  • Use YubiKey or similar for high-value accounts
  • Keep hardware keys physically secured
  • Don't register them on the Mac Mini

Replication Guide​

To harden a new Mac Mini or repeat this process:

  1. Initial setup: Sign in with Apple ID, enable iCloud (but not Keychain sync)
  2. Contacts: Import vCard from iCloud export (or Google if migrating)
  3. Keychain: Never enable iCloud Keychain sync during setup
  4. OAuth only for AI services: Authenticate Claude/OpenAI when installing agent software
  5. Verify: Passwords app should be nearly empty

Mom's Mac Mini Notes​

When hardening Charlene's Mac Mini:

  • Same process applies
  • Focus on contact cleanup (likely lots of accumulated contacts)
  • Ensure she knows Contacts are now iCloud-only
  • Document her specific Wi-Fi passwords that need to stay

References​

  • Principle of Least Privilege: Only grant access to what's actively needed
  • Defense in Depth: Multiple layers (no OAuth + no keychain sync + 2FA)
  • Threat Modeling: Focus on high-impact risks (master keys) first

Session Notes: This guide was developed during a 2-hour hardening session on January 30, 2026. Started with 187 contacts, ended with 54. Removed all passwords/passkeys except Wi-Fi. Mac Mini is now properly isolated from personal credentials.