A Russian cyber-security firm says it's found the world's first cellphone worm, but one of the largest makers of cellphones says the threat is minor.

Programmers at Kaspersky Labs in Moscow, an antivirus vendor, reported the worm this week.

The worm attacks Series 60 cellphones made by Nokia, Siemens and others that use the Symbian operating system. The worm accesses phones using their Bluetooth wireless connection.

Kaspersky programmers said a group of hackers in Spain known as 29a e-mailed the worm to them. Kaspersky's Denis Zenkin says the hackers were showing off by challenging the pros, "saying, 'Hey guys, look what we've got and you'll never defeat it.'"

The worm causes no real damage, but it does copy three files to a hidden directory, displays the word "Caribe" on the screen, and runs an infected phone's battery down by continually searching for another victim.

While this worm is essentially harmless, Zemkin says it's inevitable that soon some malicious hacker will create a more harmful virus that could delete files, steal address books – "any information that is stored on your smart phone."

McAfee, a U.S.-based computer security company, says the risk is low because a cellphone user has to deliberately activate the phone's Bluetooth connection, and accept the Caribe package before the files can be loaded into the phone.