The Callback Vulnerability
By default, if you receive a phone call on your iPhone and you miss it, a notification is displayed on your Lock Screen. Incredibly, the iOS operating system allows anyone holding your phone to tap that notification and instantly return the call, even if the device is completely locked and secured with Face ID. This means a thief or an unauthorized user can interact with your phone and immediately place a call to your contacts without knowing your passcode. You must permanently revoke this telephony privilege from the Lock Screen.
How to Disable Return Missed Calls on the Lock Screen
You can permanently secure your telephony daemon via the Face ID & Passcode settings.
- Open the Settings app on your iPhone.
- Scroll down and tap on Face ID & Passcode (or Touch ID & Passcode).
- Enter your strict device passcode to authenticate.
- Scroll down to the section labeled “Allow Access When Locked.”
- Locate the toggle switch labeled Return Missed Calls.
- Toggle this switch to the Off position (the green background will disappear).
A Hardened Communications Perimeter
The change takes effect instantly. The iPhone will completely sever the bridge connecting the Lock Screen notification interface to the Phone app’s outbound calling daemon. You can now lock your phone and leave it on a table; if you miss a call, the notification will still appear, but if a malicious actor attempts to tap it or swipe it to call the person back, the operating system will absolutely refuse to dial the number. To return a call, you are now strictly required to unlock the phone with Face ID first, guaranteeing complete control over your outbound communications.