The Convenience Vulnerability
By default, the Apple Watch is secured with a four-digit passcode. However, Apple includes a convenience feature called “Unlock with iPhone.” When enabled, if you place the locked watch on your wrist and then unlock your iPhone using Face ID or your phone’s passcode, the watch instantly unlocks itself automatically, completely bypassing the watch passcode screen. While this saves time, it is a massive security vulnerability. If someone steals both your phone and your watch while you are sleeping, and forces your thumb onto the phone screen or points the phone at your face to unlock it, the watch unlocks simultaneously. For maximum security, the two devices should remain isolated.
How to Turn Off Unlock with iPhone
You must sever this automated authentication link using the companion app on your phone.
- Open the Watch app on your iPhone.
- Ensure you are on the My Watch tab at the bottom left of the screen.
- Scroll down the main list and tap on Passcode.
- Look for the toggle switch labeled Unlock with iPhone.
- Toggle this switch to the Off position (the green background will disappear).
The Isolated Device
Once disabled, the two authentication systems operate completely independently. Whenever you take the watch off the magnetic charger and strap it to your wrist, you must manually type the four-digit passcode into the tiny watch screen to access it. Unlocking your massive iPhone will no longer grant automated backdoor access to the data stored on your wrist.