The Mabir. A worm can spread via Bluetooth connections, but more worrying is that it can reach new targets using Multimedia Message Service. MMS is the mobile technology that lets people send text messages that contain audio, video and pictures. The worm waits for MMS or regular SMS text messages to come into the infected handset, then shoots off a reply that carries the malicious file.
Given how easy it is to send messages to handsets around the world, the scope for damage with a MMS worm seems huge. No need to worry yet--F-Secure says Mabir has yet to be detected in the wild.