Several months after its first sighting, the Cabir worm that infects mobile phones has surfaced in the US.

A variant of the Cabir worm - there are several of them - was found in two Nokia handsets on display in the shop window of a store in Santa Monica, California, said Mikko Hypp"nen, director of antivirus research at F-Secure.

The worm was spotted by an engineer from rival security vendor Symantec, according to Hypp"nen. "It was purely coincidental," he said. "When the Symantec guy noticed the infected handset in the shop window, he went inside and told the owner, whose mobile phone, it turned out, was also infected."

Hypp"nen declined to name the store. Symantec did not immediately respond to a request for comment.

The US sighting brings the total number of countries in which some variant of the Cabir worm has been detected to 12, he said.

In addition to countries in Asia and Latin America, the worm has surfaced in phones in four European countries: Italy, Finland, the UK and Russia.

The Cabir worms spread between smart phones using a specially formatted Symbian Installation System (SIS) file disguised as a security management utility. Infected phones scan for vulnerable handsets using the short-range Bluetooth wireless connection, then send a file containing the worm to those phones.

To be infected by Cabir, mobile phones must be running Symbian OS with the Series 60 software and have the Bluetooth wireless feature in "discoverable" mode, making them open to new connections, according to Hypp"nen. In addition, the owner of the phone would have to press a key to dismiss a security warning about installing software of unknown origin, and then another to agree to install the file being transmitted, F-Secure said.

Users know when their phones are infected because phone batteries are rapidly consumed, he said.

At the end of last year, total shipments of Symbian-based smart phones reached 25 million, with eight handset manufacturers including Nokia, Siemens AG and Sony Ericsson Mobile Communication AB, supplying 41 phones.

Nokia, the world's largest handset manufacturer, owns slightly under 50 percent of Symbian.

At last week's 3GSM World Congress in Cannes, Symbian officials said security was a high priority of the company's latest software, Symbian OS version 9.