Facebook announced it identified stealth misinformation campaigns from Russia and Iran and shut down hundreds of accounts as part of its battle against manipulation of its platform, prompting a fresh denial from Moscow on Wednesday.
The social network said late Tuesday that it 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.
Separately, Twitter said it suspended 284 accounts "for engaging in coordinated manipulation," adding that "it appears many of these accounts originated from Iran."
"As with prior investigations, we are committed to engaging with other companies and relevant law enforcement entities," Twitter said.
For Facebook, it was the second time in less than a month that it acted against manipulation, following the shutdown in late July of 32 fake pages and accounts involved in an apparent "coordinated" effort to stoke hot-button issues ahead of November midterm US elections.
The social network giant said content from some of the pages shut down in the latest move was traced back to Iran, while others were tied to groups previously linked to Russian intelligence operations.
Zuckerberg said the latest effort involved two separate sets of campaigns, including one with ties to Iran's state-owned media and another apparently linked to Russian military intelligence services.
The accounts, some of them on Facebook-owned Instagram, were presented as being independent news or civil society groups but were actually working in coordinated efforts, 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.
- SOCIAL MEDIA 'INFLUENCE' OPERATIONS -
The Facebook investigation was prompted by a tip from cybersecurity firm FireEye regarding a collection of "Liberty Front Press" pages on the social network and other online services.
"The activity we have uncovered highlights that multiple actors continue to engage in and experiment with online, social media-driven influence operations as a means of shaping political discourse," FireEye said in a statement.
"These operations extend well beyond those conducted by Russia, which has often been the focus of research into information operations over recent years."
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.
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.
In Moscow, a government spokesman denied any manipulation campaign, telling journalists, "We don't understand what the basis is" for the accusations.
The actions by Facebook and Twitter come days after Microsoft said it seized websites linked to Russian intelligence which sought to meddle in US political debate.
Senator Mark Warner said the latest revelations were "further evidence that foreign adversaries are actively using social media to divide Americans and undermine our democratic institutions."
Facebook chief operating officer Sheryl Sandberg is among Silicon Valley executives set to take part in a September 5 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.
