Around 3,300 new malicious codes have been detected by Trend Micro between Aug 1 and Aug 20 in 2004. The malicious codes consisted mainly of trojans, back-doors and worms. According to the Trend Micro World Wide Tracking Centre, Sasser was the most prevalent virus in August with 325,409 victims and made up nearly 31% of infections in the August top 10 virus list. However, the six variants of NetSky accounted for almost 46%. In Australia, the March variant NetSky.P accounted for over 45% of August infections.