The Trojan.Mquito is not a trojanized version of the game, the hidden SMS functionality was put in the game from the beginning by the original manufacturer.
This functionality was supposed to be some kind of a copy-protecting technique, but it didn't work right and the whole functionality backfired.
According to the manufacturer, the premium rate contract for the receiving phone numbers has been terminated, so although old versions of the game still send hidden SMS messages, it only costs the nominal fee of sending the message itself.
Current versions of this game no longer have this hidden functionality, but "cracked" versions of Mosquitos still float in P2P network - and they still send these messages.
The SMS sending version of the game can still be identified by the message it shows when the game starts.
The original version will display following text, which varies a bit depending on the region.
UK VERSION This version is for the UK market only and does not work
outside the United Kingdom. Pirate copies are illegal and offenders
will be prosecuted.
The trojan version will display following modified text:
FREE VERSION This version has been cracked by SODDOM BIN LOADER
No rights reserved. Pirate copies are illegal and offenders will
have lotz of phun!!!
The difference in message has been done by modifying strings inside the game binary. The difference in the messages is the only difference between cracked and original version that we have been able to determine.
Needless to say that the 'trojan' version of the game can be found only from pirated sources. So installing such program is not recommended in the first place, as any copy that contains the SMS routine is an illegal copy.
Installation to system
The game is downloaded in Symbian installation SIS package, from where user has to install the the game manually.
The Mquito is distributed as cracked version of game Mosquitos in pirate channels, such as P2P file share networks.
When the Mquito is run it will show the dialog containing message from cracker and send SMS message to premium rate number. After sending the message the game will start normally.
The SMS sending routine is built into the binary by game developers, not inserted by crackers
The message is sent only when the game starts, and the sending routine will not be called before the Mquito is started second time.