The latest Click Fraud Index from Click Forensics is out today, and the company says that the problem is getting worse.
The index, which gathers data from 4,000 online advertisers and agencies, reports that the overall industry average click fraud rate rose to 15.8% for the second quarter of the year.
The report says that growing use of botnets is making the problem worse, with traffic from botnets doubling between Q1 and Q2.
Tom Cuthbert of Click Forensics said:
"A significant percentage of today’s click fraud traffic can be attributed to two growing areas of concern for search advertisers – traffic that comes from botnets and from parked domains or made-for-ad sites.
"Advertisers running campaigns on content networks are especially vulnerable as they are increasingly targets of this growing pool of savvy fraudsters."
Other figures from the study:
The overall average click fraud rate was 15.8%, up from 14.1% for the same period last year, and 14.8% from Q1 2007.
The average click fraud rate on content networks, including Google AdSense and the Yahoo! Publisher Network, was 25.6%, up from 21.9% for Q1 2007.
Apart from North America, most click fraud originates from France (5.1%), China (3.2%) and Australia (3%).
As covered previously, there is a dispute between Google and Click Forensics over the true rate of click fraud. The search engine has claimed that the real rate is far lower than the firm's estimates.
Google has recently opened up a little more on the issue, and recently decided to allow PPC advertisers to prevent certain IP addresses from receiving their ads, as well as giving more details on its methods of dealing with the problem.