Experts have found the first Trojan horse that can cause mobile phones crash after being affected, the CNET News reported on Wednesday.

Unlike the Trojan horses identified earlier, this new one, named Fontal.A, does not propagate over Bluetooth wireless networking connections or Multimedia Message Service (MMS), which is a mobile technology for sending text messages that can also include images, audio or video.

Instead, it is distributed via file-sharing or IRC (Internet relay chat). Other Trojan horses, or applications that appear to be legitimate but perform illicit activity when they are run, have found their way into smart phones, the report said, quoting Finnish IT security firm F-Secure.

Fontal.A affects Nokia Series 60 handsets running the Symbian operating system. The Finnish firm did not say whether any infections had been reported.

The Trojan horse tries to install a corrupted file, called " Kill Saddam By OID500.sis," into the infected phones, causing it to fail at the next reboot, F-Secure said. If the handset is rebooted, it gets stuck and can't be used until it is disinfected.

It also damages the application manager, preventing new programs from being installed, and stopping the Trojan itself from being uninstalled. The only fix is to reformat the phone operating system, which will cause all data on the handset to be lost, F- Secure said.

The only way to avoid Fontal.A and other Trojans is to download files only from known or trusted sources, security experts said.

Although experts have warned that virus, worms, and Trojans will spread from the computer world to mobile phones and make up real threats in this year, it is the first time they found a rogue program capable of destroying the phone operating system.

Earlier, antivirus researchers have reported another new Trojan horse that could prove to be a pervasive threat. The malicious software, dubbed "CommWarrior" and described as a virus by some antivirus companies, is also aimed at the Symbian operating system running on Nokia Series 60 handsets.

The CommWarrior attempts to spread by sending messages via Bluetooth wireless connections and MMS. As MMS can be used to send text messages worldwide, the CommWarrior has a greater reach and so could be forewarded more rapidly, the researchers said.

After infecting the telephone directory software in the handsets, it randomly selects one directory profile at a time and sends a copy of itself to that person. It can use more than 20 different messages to try to lure users into opening its file, including text designed to look like legitimate software updates from Symbian, or even pornographic photographs.

The CommWarrior can spread more quickly and widely, but the Fontal.A is more destructive to mobile handsets, experts concluded.