"I Hacked Your Device" is a scam (a spam email campaign) that According to these scammers, they planted a malicious program on an adult website that was visited by Free scanner checks if your computer is infected.
In May 2015, the adult hookup site Adult Friend Finder was hacked and nearly 4 million records dumped publicly. The data dump included extremely sensitive.
There are additional variations, often playing up the adult website angle, or even . If My Email Account is Hacked, What Kinds of Things Should I Check?.