Reject unknown sign-in attempts
When you sign in on a new device, you get a notification on your other trusted devices. The notification includes a map of the new device’s location. This notification can appear on any trusted device; an iPhone, iPad, or Mac.
This is an approximate location based on the IP address or network that the device is currently using, rather than the exact location of the device.
If you see a notification that your Apple ID is being used to sign in on a new device and you’re not signing in, tap Don’t Allow to block the sign-in attempt. You may also want to capture a screenshot of the notification before dismissing it.
See Record suspicious activity.
If you think your Apple ID might be compromised, see Keep your Apple ID secure and remove unknown devices.