The overall click fraud rate for the pay-per-click (PPC) industry averaged 16.6 percent in the fourth quarter of 2007.

The rate of click fraud for all of 2007 was up 15 percent over 2006 levels, according to Click Forensics, citing data from the Click Fraud Index, MarketingCharts reports.

Key findings from data reported for the fourth quarter:

• The overall industry average click fraud rate rose to 16.6 percent for 4Q07. That's up from the 14.2 percent click fraud rate in the fourth quarter of 2006 and 16.2 percent in 3Q07.

• The average click fraud rate of PPC advertisements appearing on search engine content networks (such as Google AdSense and the Yahoo Publisher Network, but also smaller players) was 28.3 percent in Q4. That's up from the 19.2 percent average click fraud rate for the same quarter in 2006 and 28.1 percent for 3Q07.

• Q4click fraud traffic from botnets was 15 percent higher than click fraud traffic from botnets in Q3.
• In Q4, the greatest percentage of click fraud originating from countries outside North America came from India (4.3 percent) Germany (3.9 percent) and South Korea (3.7 percent).

About the data: The Click Fraud Index monitors and reports on data gathered from the Click Fraud Network, which includes more than 4,000 online advertisers and agencies. Click fraud data is tracked and published on a quarterly basis for specific search providers, industries and trends.