MalwareMalware lingers on for months on infected PCs
New study says that if computer systems are not disinfected quickly after infection, then infection tends to linger around indefinitely, possibly until the point users exchange compromised boxes for new machines
Talk of infusing the term “resident evil” with new meaning: Malware stays around on infected PCs far longer than previously thought, according to the latest research from Trend Micro. Previous estimates suggested that a compromised machine remains infected for approximately six weeks. Based on an analysis of around 100 million compromised IPs, Trend Micro concludes that many infected IPs are infected (or repeatedly infected) for more than two years, with a median infection length of 300 days. Four in five compromised machines are infected for more than a month.
A graph from Trend Micro suggests that if systems are not disinfected quickly then infection tends to linger around indefinitely, possibly until the point users exchange compromised boxes for new machines.
John Leyden writes that Trend’s study also looked at the botnet landscape. Three strains of botnet agent — Koobface, Zeus/Zbot and Ilomo/Clampi — are causing the most damage in terms of identity theft.
The Koobface botnet, for example, has co-opted around 51,000 machines into its ranks. Koobface uses between five and six command and control centers (C&C) to control these zombie clients at any one time. If a particular control domain is taken down by a particular provider, then botnet herders behind the malware establishes a new command outpost elsewhere. Between the middle of March and mid-August 2009, Trend Micro recorded around 46 Koobface control domains.
Trend’s stats do not cover dormant infections by the Conficker worm. Stats from the Anti-Conficker Working Group suggest the malware is still resident on more than five million compromised machines.
