The first known cell-phone virus, Cabir, is entirely innocuous. All it does is sit in the phone and try to spread itself. Other cell-phone viruses, however, are not as harmless.
A virus might access and/or delete all of the contact information and calendar entries in your phone. It might send an infected MMS message to every number in your phone book -- and MMS messages typically cost money to send, so you're actually paying to send a virus to all of your friends, family members and business associates. On the worst-case-scenario end, it might delete or lock up certain phone applications or crash your phone completely so it's useless. Some reported viruses and their vital statistics are listed below.
As you can see from the above descriptions, cell-phone viruses have gotten a lot more harmful since the Cabir worm landed in the hands of researchers in 2004. But on the bright side, there are some steps you can take to protect your phone.