Depends on version of phone but usually either receiving some message (there has been some zero-click iMessage exploits) or clicking a link on one. for example

Depends on version of phone but usually either receiving some message (there has been some zero-click iMessage exploits) or clicking a link on one. for example https://citizenlab.ca/2021/09/forcedentry-nso-group-imessage-zero-click-exploit-captured-in-the-wild/ https://citizenlab.ca/2021/09/forcedentry-nso-group-imessage...