A month before the 2016 U.S. presidential election, a rumor spread on Facebook. People were sharing a viral gimmick familiar to email spammers: Copy and paste this message to all your friends, or Facebook will share your private information. The hoax took off, particularly in pockets of the U.S. and the Philippines.

Inside Facebook Inc.’s Menlo Park, California, headquarters, a small group of staffers watched this rumor gain traction using a special software program they called Stormchaser. The tool was designed to track hoaxes and “memes” – silly, often untrue internet missives – about Facebook on the social network and other company-owned services including WhatsApp.

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Source: How Facebook Fought Fake News About Facebook – Bloomberg