Reject unknown sign-in attempts
When two-factor authentication is turned on and a sign-in attempt occurs on a new device, you get a notification on your other trusted devices. The notification includes a map that shows the new device’s location. This notification can appear on any trusted iPhone, iPad, or Mac.
The location of the sign-in attempt is approximate, based on the IP address or network that the device is currently using, rather than on the exact location of the device.
If you see a notification that your Apple Account is being used to sign in on a new device you don’t recognize, select Don’t Allow to block the sign-in attempt.
IMPORTANT: You may want to capture a screenshot of the notification before dismissing it. See Record suspicious activity.
If you think your Apple Account might be compromised, see Keep your Apple Account secure and remove unknown devices.