Is it true that a no one can use your iphone if locked, icloud logged in?

[applet]

l was told by Genius in Edinburgh apple store that even if someone took possession of your iphone, they couldn't do anything with it even if all was wiped out, as the icloud account would have to be logged in before any changes can be made. this sounds too good to be true. does it also apply to macbooks, ipads if locked and logged into persons icloud? thanks

 

[MacsBug]

Yes and No.... They should have told you that you need to have Find my Phone enabled. Once thats enabled then if someone steals your iPhone then they cannot erase it or reuse it without having access to your AppleID account.

On a Mac the same applies if you have a Mac with a M series processor. You would need to turn on Find my Mac.

 

[Rodananne]

Find My is enabled by Default when you are signed into iCloud, it is found in Settings > Apple ID or just Search for "Find My" in Settings.
Once that is on your Apple ID and Password is required to turn it off. You cannot erase any Apple device without turning it off.