Click fraud, an issue that Google and many other search providers have gone to court over, has long plagued the online advertising industry. Unfortunately for companies like Google and Yahoo, the problem is just getting worse. Despite their claims that they are combating it better than ever before, the rate of click fraud, according to the Click Fraud Index, the rate of fraud has increased an average of 14.8%. This is the highest gain in quite a while, and now more than a fifth of all clicks are considered to be fraudulent.

Both Google and Yahoo don't exactly agree with these figures, with Google claiming their rates are below 10% and Yahoo claiming they are below 15%. The big issue, it seems, like with other methods of fraud, is that as the tools to prevent it become better, the methods used by the criminals are refined and new techniques are used. It's an ever-evolving battle, such as with email viruses, and for the moment it seems the good guys are on the losing end of it.