Identifying linked devices on an Apple Account

Re: "Identifying linked devices on an Apple Account"

You can: Check your Apple Account device list to find where you’re signed in - Apple Support

Eg: says:

"Learn which devices appear in your Apple Account device list,

how to find your device details,

and how to remove a device".

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Re: "How do I know if someone is linked to my device"

iOS 16 introduced Safety Check for an iPhone with iOS 16 or later - Apple Support

Eg: says:

"Safety Check — a feature available through the Settings app on an iPhone with iOS 16 or later — allows you to quickly review, update and stop sharing your information with individual people and apps."

Keeping your device updated to the newest compatible iOS version seems to provide the best security.

Overview: Privacy - Control - Apple

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More info. is available if needed:

See how to: Keep your Apple Account secure on iPhone - Apple Support

See what to do: If you think your Apple Account has been compromised - Apple Support

Eg: says:

"If you’re concerned that an unauthorised person may have access to your Apple Account, these steps can help you regain control of your account." see above article for details.

iOS 18: See how to: Control what you share on iPhone - Apple Support