A iPhone worm is reported to have broken out, that targets owners who have jailbroken their iPhones but not changed the default password after installing SSH. According to Mashable is the worm not harmful. It shows a message saying your iPhone has been hacked and changes your background to a photo of Rick Astley.

First iPhone Worm

Here is a Instruction, that shows how to change the default password:

1. Go to Cydia
2. Install Mobile Terminal app
3. Open Terminal app
4. Type passwd and hit enter
5. Enter alpine for your old password and enter new password twice

First iPhone Worm