Facebook said Tuesday it stopped stealth misinformation campaigns from Iran and Russia, shutting down accounts as part of its battle against fake news ahead of elections in the United States and elsewhere.
Facebook removed more than 650 pages, groups and accounts identified as "networks of accounts misleading people about what they were doing," according to chief executive Mark Zuckerberg.
While the investigation was ongoing, and US law enforcement notified, content from some of the pages was traced back to Iran and from others linked to groups previously linked to Russian intelligence operations, the social network said.
"We believe they were parts of two sets of campaigns," Zuckerberg said.
The accounts, some of them at Facebook-owned Instagram, were presented as being independent news or civil society groups but were actually working in coordinated efforts, social network firm executives said in a briefing with reporters.
Content posted by accounts targeted Facebook users in Britain, Latin America, the Middle East and the US, according to head of cybersecurity policy Nathaniel Gleicher.
He said that posts by the involved accounts were still being scrutinized and their goals were unclear at this point.
The Facebook investigation was prompted by a tip from cybersecurity firm FireEye regarding a collection of "Liberty Front Press" pages at the social network and other online services.
Facebook linked the pages to Iranian state media through publicly available website registration information, computer addresses and information about account administrators, according to Gleicher.
Among the accounts was one from "Quest 4 Truth" claiming to be an independent Iranian media organization. It was linked to Press TV, an English-language news network affiliated with Iranian state media, Gleicher said.
The first "Liberty Front Press" accounts found were at Facebook were created in 2013 and posted primarily political content focused on the Middle East along with Britain, Latin America and the US.
Russian military tie
Facebook also removed a set of pages and accounts linked to sources the US government previously identified as Russian military services, according to Gleicher.
"While these are some of the same bad actors we removed for cybersecurity attacks before the 2016 US election, this more recent activity focused on politics in Syria and Ukraine," Gleicher said.
The accounts were associated with Inside Syria Media Center, which the Atlantic Council and other organizations have identified as covertly spreading pro-Russian and pro-Assad content.
US Senator Richard Burr, a Republican who chairs the select committee on intelligence, said that the halted campaigns further prove that "the goal of these foreign social media campaigns is to sow discord" and "that Russia is not the only hostile foreign actor developing this capability."
Facebook chief operating officer Sheryl Sandberg is among Silicon Valley executives set to take part in a 5 September Senate hearing about foreign efforts to use social media platforms to influence elections.
"We get that 2018 is a very important election year, not just in the US," Zuckerberg responded when asked about the upcoming hearing.
"So this is really serious. This is a top priority for the company."
In July, Facebook shut down more than 30 fake pages and accounts involved in what appeared to be a "coordinated" attempt to sway public opinion on political issues ahead of November midterm elections, but did not identify the source.
It said the "bad actor" accounts on the world's biggest social network and its photo-sharing site Instagram could not be tied to Russia, which used the platform to spread disinformation ahead of the 2016 US presidential election.