Google has announced a new feature that aims to lift the lid on 'click fraud'. 

Advertisers using Google's AdWords system can now run account performance reports that include data about invalid clicks.

As well as seeing the total number of invalid clicks, advertisers can also see the ratio of invalid to valid clicks during a given period. 

Click fraud happens when machines or people click on adverts with the aim of driving up costs for the advertiser. Companies pay for online ads based on the number of hits each ad receives.

Google's data will now show all the malicious activity that the search company has identified and removed from the advertisers' accounts.

Advertisers can run the feature in annual, quarterly, weekly and daily reports. Hourly reports are not yet available, and data only goes back to 1 January 2006.

Google explained that click fraud has become an increasingly troublesome area. "One of the controversial issues related to the topic of click fraud has been estimating how big the problem is," wrote Google business product manager Shuman Ghosemajumder in his blog.

"This new tool will make estimating invalid click activity much easier." 

The tool is likely to save Google time and money investigating click fraud, and may also save costly days in court. Google, Yahoo and AOL have all been sued by advertisers claiming that they have been charged for invalid clicks.