Hackers planted the virus in bogus game files, which are being illegally downloaded from P2P networks by those keen to experience the game without purchasing it.
John Safa, chief technical officer of DriveSentry, said: "People are exploiting the popularity of GTA IV in a way which could bring mayhem to the internet."
"Hackers are increasingly sophisticated in the way they disrupt the web. They will piggyback on anything popular to wreak havoc. The only thing that many gamers can think of at the moment is GTA IV and hackers are using that interest to try to generate chaos as quickly as they can," he added.
Former hacker Safa highlighted that within two minutes of logging on to P2P network Limewire he found evidence of Trojan viruses disguised as GTA IV files.
"Such computer viruses have the potential to wipe out or steal sensitive information such as a user's bank details or wipe out important files. Some of these links were offering free downloads for the PC version of Grand Theft Auto IV even though it is not available yet."
"I would urge anybody to tread very carefully around these links, as some links are designed to look official -- or even better invest in a good anti-virus package that is capable of protection from the latest threats for their computer."
This story, "Bogus Grand Theft Auto IV Contains Trojan" was originally published by PC Advisor (UK).