Hi,
The Trojan.Mos virus is included on the MOSQUITO game. When you install this game, (maybe not from the original one) the virus will also be installed on your system's folder.
The affect of this virus is it will use your SMS gateway to send messages to a high cost number, hence you will be charged.
When Trojan.Mos is executed, it performs the following actions:
Copies itself to \system\apps\Mosquitos\Mosquitos.app.
Sends an SMS message to a high-cost phone number.
Starts a game that is similar to a popular game known as Mosquitos produced by Ojom.
Knowing that there is another virus against series 60 phone is frightening.
Visit the advisory by symantec below for details:
http://securityresponse.symantec.com/avcenter/venc/data/trojan.mos.html