Botnets are being used for Google Adword click fraud, according to security watchers.

The SANS Institute has uncovered evidence that networks of compromised PCs are being used to click on banner ads, generating revenue for unscrupulous publishers.

Pay-per-click schemes such as Google Adsense have programs to detect fraudulent clicks and suspend publishers implicated in click fraud. In an effort to disguise bogus visits, these publishers have begun hiring botnets to slip under the radar of fraud detection programs.

The "bottom line is that the advertiser pays in exchange for a bot visiting him", the SANS Institute reports.

Read more about Adsense click fraud involving botnets at http://www.theregister.co.uk/2006/05/15/google_adword_scam/.