Readers of this blog know that click fraud is an issue we take very seriously at Google. We throw out a significant percentage of ad clicks (on average in the single digits) every day to protect our advertisers. Because of our investment in click fraud protection systems, we are able to manage this issue very well and prevent it from having an impact on the vast majority of AdWords advertisers.

However, click fraud is real, and it’s definitely one of the main concerns of advertisers who contact myself and our Click Quality team. But in the click fraud sessions at the Search Engine Strategies conferences and elsewhere, I often hear from advertisers who tell me that they don’t know how to correctly diagnose whether they’ve been affected by click fraud, or how to contact Google to request an investigation.

Well, there’s a great post on the AdWords blog about just that from Julian, a long-time member of our Click Quality team. In it, he describes many common cases which can actually be misdiagnosed as click fraud – such as normal traffic or ROI fluctuations (caused by other sources), web log discrepancies due to technical issues, or multiple clicks from the same IP address due to large shared ISP proxies. The Click Quality team helps diagnose these cases every day, but you as an advertiser can diagnose them too. The most important thing to remember is that undetected click fraud shows up as a drop in ROI that you can’t explain because of other causes. The more carefully and granularly you track your campaign, the better you can optimize its performance – including managing issues related to click fraud.

In the rare event you find that your campaign may have been affected by undetected click fraud, our Click Quality team definitely wants to hear from you. There’s a link at the end of the post to the form you can use to contact them, which I’ll repeat for good measure here.