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.