First Cabir, then Mabir. Now a SIS file trojan - Fontal.A - that installs a corrupted Font file into infected mobile devices, thus causing them to fail at next reboot, has been identified by Finnish virus specialists F-Secure. It potentially affects Series 60 smartphones running Symbian OS.

A very disturbing sentence in F-Secure's alert about the trojan reads: "If a phone is infected with Fontal.A, it must not be rebooted as the trojan will prevent the phone from booting again. If the phone is rebooted, it will try to boot, but will be forever stuck on phone startup and cannot be used."

This news comes hard on the heels of F-Secure's report just two days ago about the Mabir worm.

A trojan differs from a worm in that it isn't self-propagating. But that will come as cold comfort to those affected, since the only known way to disinfect a phone that is infected with Fontal (and is rebooted) is to reformat the phone. Bye bye address book.

There will be a special place in hell reserved for Mobile hackers.

• New Cellphone Virus, Mabir, Attacks Symbian Series 60 Devices