Malicious programs that can delete address books. Junk messages that flood a cell phone's inbox. Stealthy code that uses Bluetooth wireless technology to sneak onto handsets. Scared yet? Security experts say plagues like these will target mobile phones, but others contend cell phone viruses are the tech equivalent of smallpox: To the best of anyone's knowledge, they exist only in labs.

"We've had no reports of people actually seeing these viruses in their daily use," said Graham Cluley, a senior technology consultant with London's Sophos PLC. "The only reports we've seen documented are antivirus researchers sending them to each other in their labs."