Facebook is in more hot water because of its advertising business.
The world's largest social network is reviewing its ad policies after an investigation published by ProPublica on Thursday revealed marketers could specifically target their ads to reach anti-Semites.
Ads could be directed toward Facebook users who fell under that ad categories "Jew hater," "How to burn jews" and "History of 'why jews ruin the world.'" Facebook says it has since removed those categories.
Like most of the tech industry's ad platforms, Facebook's advertising software is mostly automated. The categories are generated based on the expressed interests of users, or what Facebook can infer about users' interests. Advertisers can target people based on their self-reported information, like education or employer. The anti-Semitic categories were generated after people entered things like "Jew hater" into their field of study.
ProPublica said the number of people who fell into those ad categories was too small to buy ads. For example, the "Jew hater" category contained 2,300 people, out of Facebook's 2 billion monthly users.
Facebook's ad business has become a hot-button topic. Last week, theit sold $100,000 worth of ads to inauthentic accounts likely linked to Russia during the election. The company has also been grappling with how to deal with its massive influence and power, as it faces criticism for its handling of false news spreading on the site.
Facebook isn't the only tech giant that's courted controversy over its automated ad platforms. Earlier this year, Google faced an advertiser boycott after ads appeared next to extremist YouTube videos.
"Our community standards strictly prohibit attacking people based on their protected characteristics, including religion, and we prohibit advertisers from discriminating against people based on religion and other attributes," Rob Leathern, product management director at Facebook, said in a statement. "However, there are times where content is surfaced on our platform that violates our standards.
"We know we have more work to do, so we're also building new guardrails in our product and review processes to prevent other issues like this from happening in the future," he said.
One of those guardrails could be to add more reviews of fields before they show up in ads creation, according to a person familiar with Facebook's thinking.
Jonathan Greenblatt, CEO of the Anti-Defamation League, commended Facebook for taking action but said he'd follow up with the social network.
"It was shocking to read about this practice on Facebook, and we are glad Facebook ended it," he said in a statement. "I will be calling Facebook as soon as possible for an explanation of what went on, and will work with them to root out anti-Semitism and hate online."
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