The first half of 2004 saw a huge increase in zombie PCs. Also called bots, their average numbers monitored by security firm Symantec rose between January and June from under 2,000 to more than 30,000 per day - peaking at 75,000 on one day.
Botnets are computers infected by worms or Trojans and taken over surreptitiously by hackers and brought into networks to send spam, more viruses, or launch denial of service attacks.
Richard Archdeacon, Symantec's director of technical services, said: "Bot networks create unique problems for organisations and individual PC users as systems can be automatically upgraded with new exploits very quickly, allowing attackers to outpace efforts to patch or download security updates. We saw a steady increase in the number of bots during the reporting period. Variants of the 'Gaobot' family alone accounted for 67,000 submissions."
The latest edition of Symantec's global Internet Security Threat Report, notes that attacks against web application technologies are increasingly popular, mainly because security weaknesses are relatively easy to find. Symantec also reports that the time between the announcement of a vulnerability and the release of associated exploit code is becoming extremely short. The average vulnerability-to-exploit window is down to just 5.8 days. ®