ESET found that 13.29 per cent of malware detections from a sample of over 10 million systems worldwide were classified as 'Win32/PSW.OnLineGames'.
Although this figure is significantly down from last month's 18 per cent, ESET warned that this "does not necessarily" mean a drop in the number of infections.
Win32/PSW.OnLineGames is a family of Trojans with key-logging and rootkit capabilities that gathers information relating to online gaming.
"For-profit malware is still the biggest growth area in virtual world criminalisation, but we also see a range of other types of attack in these environments," said David Harley, research author at ESET.
"Attacks such as 'grey goo', a form of replicative malware, and 'griefing', where an avatar is used to interfere with the environment and harass other players, have plagued sites like Second Life.
"Although generally disruptive rather than stealing information, they are extremely annoying and sometimes distressing for other users, and something developers are keen to avoid."
Other notable malware in this month's top 10 threats detected by ESET was SWF/Exploit.CVE-2007-0071, which takes advantage of a vulnerability in Adobe Flash Player up to and including version 220.127.116.11.
Using this exploit a remote attacker is able to execute arbitrary code using a specifically formulated Shockwave Flash file. A patch has been available from Adobe since 8 April.
Trojans stop play for web gamers
By Robert Jaques on Jul 4, 2008 2:08AM