The Proximity Exploit
Apple devices feature a Continuity protocol that allows your Apple Watch to automatically unlock your macOS computer. By default, if this feature is enabled, simply sitting down in front of your locked Mac while wearing your unlocked Apple Watch will instantly bypass the Mac’s login screen without requiring a password or Touch ID. While highly convenient, this proximity-based authentication is a massive security risk in open office environments. If you walk away from your desk but remain within a few meters (e.g., getting coffee nearby), a coworker can sit at your Mac, wake it up, and the Bluetooth connection to your watch will instantly authenticate them, granting full access to your hard drive. You must paralyze this auto-unlock bridge.
How to Disable Auto Unlock on Mac
You must sever the proximity authentication bridge from the receiving end (the Mac) via its System Settings.
- Open the System Settings app on your Mac (the gear icon in the Dock or Apple menu).
- In the left-hand sidebar, click on Touch ID & Password (or Login Password on older Macs).
- Scroll down to the “Apple Watch” section.
- Locate the toggle switch next to your specific Apple Watch’s name (labeled “Use your Apple Watch to unlock your applications and your Mac”).
- Toggle this switch to the Off position.
- You will be required to enter your Mac’s administrator password to confirm the security downgrade.
Strict Cryptographic Authentication
The change is instantaneous. macOS will completely terminate the background Bluetooth LE daemon responsible for polling your wrist for cryptographic tokens. The operating system is now mathematically decoupled from your Apple Watch for authentication purposes. You can now sit directly in front of your computer, and the Mac will absolutely refuse to unlock itself. To access your desktop, you are now strictly required to use your biometric fingerprint or type your complex alphanumeric password, guaranteeing absolute physical security for your local filesystem.