Click Forensics today reported that the overall industry average click fraud rate for pay-per-click (PPC) advertising was 17.1 percent in the fourth quarter of 2008, up from 16.0 percent in the third quarter of 2008. The rate was 16.6 percent in the fourth quarter of 2007. The rate of click fraud for PPC advertisements appearing on search engine content networks, including Google AdSense and the Yahoo Publisher Network, was significantly higher than the overall, representing 28.2 percent of clicks during the fourth quarter of 2008. Botnets made up over 31.4 of the click fraud during the quarter. Click Forensics gathers the data from online advertising campaigns for both large and small companies