Towns wanted to make the point that people should change their default iPhone passwords, especially if they're using SSH . "A lot of people especially at first thanked me," he said. "I think most people are relieved its not out to destroy their phone. I have had a few people abuse me though."

He didn't really consider the possible legal ramifications of releasing the code, something he said was "quite naive of me," Towns said.

Once the worm adds the Rick Astley wallpaper, it disables the iPhone's SSH daemon and then looks around and then looks around on the Internet for other vulnerable iPhones to infect.

Tricking victims into playing a video or looking at a picture of Rick Astley -- best known for his hit -- is a popular Internet prank called Rickrolling.

It's not clear how many people have been affected by the worm, but Towns said that his phone alone infected about 100 other devices.