A new mobile virus is spreading by pretending to be a returned message from a friend.

The Mabir.A virus affects Symbian Series 60 phones and is sufficiently similar to the first mobile phone virus Cabir to make some experts think it has the same author. But rather than just relying on Bluetooth to spread Mabir.A uses incoming messages to spread, making it potentially more virulent.

"The MMS spreading function of Mabir.A uses a new social engineering technique," said Jarno Niemela, a researcher at antivirus specialist F-Secure's laboratory.

"Instead of just reading all phone numbers from the local address book, the Mabir.A listens for any SMS or MMS messages that arrive to the phone. When a message arrives, Mabir.A sends itself as MMS message to the sending phone number, thus posing as a reply to whatever message was sent to the infected phone."

This ability to spread over long distances via popular messaging services in combination with other transmission techniques opens up the prospect for much wider outbreaks than if the virus relied on radio transmission alone.

While the virus can spread by Bluetooth there appears to be a flaw in the virus program. If an infected phone identifies another device on Bluetooth which then moves out of range the phone will try and reacquire the same device rather than looking for others.

So far the company has found over 20 mobile phone viruses in the wild.