The click fraud rate was 16.2 percent for Q2 2008, down a smidgen from the first quarter of this year, but still higher than the same period last year.

The Click Fraud Index, released by Click Forensics, states that outside the USA/Canada, the most prevalent sources of PPC fraud came from China (4.3 percent), Russia (3.5 percent), and France (3.2 percent).

A disturbing trend has been the increase of botnet related click fraud, which exceeded 25 percent of all click fraud traffic in Q2 2008. Botnet traffic can be difficult to detect as it comes from multiple sources.

Basically what happens is that malware is installed on unsuspecting folks’ computers when they open infected attachments and files; then those computers then become “zombies” which can be controlled by the botnet master to do whatever he or she wishes; e.g. crank out spam or to appear to click on PPC ads via a clickbot.

If you’re interested in learning more about botnet related click fraud, Google’s Click Quality and Security Teams published a paper called “The Anatomy of Clickbot.A” (PDF) which makes for interesting reading.

Just a bit about the Click Fraud Index - it’s based on data gathered from the Click Fraud Network, which over 4,000 online advertisers and agencies have joined. The Click Fraud Network offers free PPC fraud reporting and a monitoring service where advertisers can track up to 100,000 paid clicks each month.