iPhone users across Australia are among the first to be infected with the world's first in-the-wild worm. This worm called "ikee", changes the phone's background picture to the 1980's singer Rick Astley and then tries to infect other iPhones on the network. The Wallpaper also has the the message "ikee is never going to give you up".
This worm tries to spread to other iPhones using SSH which comes pre-installed but disabed on the default iPhone. So ineffect only users who have 'Jailbroken' their phone and have enabled SSH are likely to be affected. The worm also makes use of the fact that Apple ships its iPhones with the same root password for SSH on every iPhone and if the user enables SSH and leaves the Default password on, it renders the phone vulnerable to attack.
Infection seems to be confined to Australia at the moment, though there are unconfirmed reports of Ikee in Thailand and Japan.