By David Pierson

Los Angeles Times

Amid mounting pressure, Facebook Inc. said it would block websites that publish fake news from accessing its advertising services.

The announcement Monday came hours after Alphabet Inc.’s Google said it would also bar fake news sites from using its advertising networks.

The companies faced a backlash for allowing the spread of phony news articles during the presidential campaign season, leading to charges that the content helped influence the outcome of last week’s election.

The move to restrict fake news sites from utilizing Facebook’s advertising tools comes days after Facebook Chief Executive Mark Zuckerberg said it was a “crazy idea” to think the social network could have influenced the election. Facebook characterized the shift as a clarification of existing policies.

Fake news sites have reportedly enriched themselves by creating content that has spread virally on Facebook and Google. BuzzFeed, for example, reported on teens in Macedonia responsible for making hundreds of politically charged make-believe articles for American audiences and reaping the ad dollars that ensued.

Google, meanwhile, featured a story at the top of its search results Sunday claiming Donald Trump won the popular vote. He did not.

Though Facebook and Google both dominate the digital advertising market, fake news sites can still generate ad revenue through other smaller ad networks. And they can still dominate users’ newsfeeds if the articles go viral.

As technology companies rather than media companies, the two Silicon Valley giants have long argued they are not responsible for the content their users publish. That viewpoint is protected by Section 230 of the Communications Decency Act.