According to a new blog post, Google has decided to fight unwanted and potentially malicious ads that appear on legitimate websites. After receiving nearly 300,000 complaints from users of its Chrome web browser, Google is adding automated filters to DoubleClick Bid Manager to create blacklists. Google owns the DoubleClick technology used by advertisers to manage digital ad campaigns on behalf of websites. Google gives the example of The New York Times, whose website was showing ads the publisher didn't know about. Ad injectors were hijacking legitimate ads and replacing the ones that were originally intended to run on the website. The unwanted ads sometimes contain malicious code presented through Chrome. If the user clicked the wrong button, they could run harmful code.

The result of Google's action is a blacklisting of 1.4% of the ad inventory managed through DoubleClick Bid Manager. But the company found that the percentage of injected ads varied wildly across different ad exchanges, with one having over 15% of its ads blocked by Google's new filter.