"Advertising helps fund the digital world we love today... but this vibrant ecosystem only flourishes if marketers can buy media online with the confidence that their ads are reaching real people, that results they see are based on actual interest," said VP Display Advertising at Google, Neal Mohan.

Mohan said in a blog post that with the acquisition "our immediate priority is to include their fraud detection technology in our video and display ads products, where they will complement our existing efforts."

"By including spider.io's fraud-fighting expertise in our products, we can scale our efforts to weed out bad actors and improve the entire digital ecosystem."

Mohan also said in the blog post that last year Google turned down millions of applications from sites looking to join its network because it suspected them of fraud.

Advertising is one of Google's core revenue streams; 84 per cent of its $US59.8 billion in 2013 revenues came from advertisers.

Terms of this deal were not disclosed.