The world's first iPhone virus is reported to be in the wild, targeting users who have cracked, or jailbroken, their phone.

The virus, which so far appears to be confined to Australia, changes the users wallpaper to an image of 1980s pop star Rick Astley, and displays the message Ikee is never gonna give you up.

Only those users who have cracked, or jailbroken, their phones and not changed their passwords from the default "alpine" can be affected.

Security firm Sophos said that once in place, the worm attempts to find other iPhones on the mobile phone network that are similarly vulnerable, and installs itself on them.