Mobile phones infected with the Cabir virus have turned up in Japan and France, bringing the number of countries where Cabir infections have been reported to 16.

But Cabir remains slow-spreading and relatively rare that is unlikely to affect most mobile phone users, said Mikko Hypp"nen, manager of anti-virus research at F-Secure.

Cabir spreads on phones that run the Symbian operating system and are equipped with Bluetooth wireless connections, including Series 60 phones from a number of manufacturers, such as Siemens, Nokia and others. The virus first appeared last June as a "proof of concept" released by virus writing group 29a.

Cabir does not install malicious software on machines it infects, but does modify the configuration of infected phones, copy itself into hidden directories on the phones and display "Caribe" or "Caribe-VZ-29A" on the screen, F-Secure said.

In August 2004, the first Cabir infections were first reported in the Philippines. Since then, the virus spread from to Singapore, the United Arab Emirates, China, India and 12 other countries. The first Cabir infections in the US were reported in February.

Travellers who contract Cabir in a foreign country, then return home with it on their phone are responsible for the virus' transcontinental spread, Hypp"nen said.

Despite its global reach, Cabir is ineffective at spreading, especially when compared to its virulent cousins that spread using e-mail or from machine to machine on the Internet, Hypp"nen said.

"The fact that we're seeing these infections doesn't mean much. Cabir is a lousy spreader compared to any e-mail or network virus. This virus has been around nine months and has spread to just 16 countries. Any e-mail worm could do that in 10 minutes," he said.

To get infected, mobile phones must be running the correct version of the Symbian operating system, have the Bluetooth wireless communications feature enabled and set to listen for other Bluetooth devices, and be within broadcast range of a phone infected with Cabir. Even then, the phone's owner must click multiple times to download the Cabir file and install it on their phone, according to F-Secure.

However, Cabir also proves that mobile devices are an effective platform for distributing malicious software. A virus that spread through mobile devices using the popular SMS technology or used a phone's address book to locate victims could spread much faster.