The Department of Justice's special counsel Robert Mueller and his office have interviewed at least one member of Facebook's team that was associated with President Trump's 2016 presidential campaign, according to a person familiar with the matter.

The interview was part of Mueller's probe into Russian interference in the 2016 election and what role, if any, the Trump campaign played in that interference. Facebook and other social platforms have emerged as a key part of that investigation, not only because the company embedded staff with the San Antonio–based digital team working on Trump's campaign but also because it sold more than 3,000 Facebook and Instagram ads to fake accounts linked to the Russian propaganda group Internet Research Agency. All in, content shared by those accounts reached 126 million Facebook users, including more than 62,000 of whom signed up to attend events organized by those fake accounts.

A spokesperson for the special counsel's office declined WIRED's request for comment.

Mueller's team speaking with a Facebook employee does not necessarily implicate Facebook in any wrongdoing. It's natural that a company not only close to the campaign but also directly impacted by Russian active members would be on Mueller's radar.

Since Facebook began sharing details last fall about the extent of Russian influence on the platform, speculation has swirled about whether the Trump campaign seeded information to those trolls that may have helped them better target their ads. Facebook has repeatedly stated the Internet Research Agency ads used "rudimentary" targeting, and did not target specific lists of voters. In newly released written responses to questions asked during a congressional hearing in November, Facebook said, "We have seen only what appears to be insignificant overlap between the targeting and content used by the IRA and that used by the Trump campaign."

It's natural that a company not only close to the campaign, but also directly impacted by Russian active members, would be on Mueller's radar.

The Mueller investigation has scrutinized more tech companies than just Facebook. The special counsel asked Cambridge Analytica, a company that provided data analytics for the Trump campaign and also embedded staff in San Antonio, to provide email records. Among the curiosities of Cambridge Analytica's involvement in the campaign is that its CEO, Alexander Nix, reportedly contacted WikiLeaks founder Julian Assange during the election in hopes of collaborating on the organization and release of hacked emails related to Hillary Clinton. US intelligence agencies say that Russian actors stole those emails, creating a link between Mueller's investigation and Nix's actions. According to a Cambridge spokesperson, the company did reach out to the speakers bureau that represents Assange, after he claimed to possess leaked material related to the election on television. The speakers bureau denied the request, according to the spokesperson. "No one from Cambridge Analytica has ever been in ​direct ​contact with ​​Wikileaks," the spokesperson said.1 Cambridge declined to comment on Mueller's investigation.

Both Twitter and Google deployed staff to San Antonio to work with the Trump campaign as well. (Google, Facebook, and Twitter all worked with the Clinton campaign, but did not embed with that team.) They also both sold ads to the Internet Research Agency. Last week, Twitter reported that it is alerting 677,775 people that they followed, retweeted, or liked tweets by fake Russian accounts—tweets that collectively received roughly 288 million views. Twitter declined to comment on whether Mueller has interviewed anyone from its staff.

Google also did not immediately respond to WIRED's request for comment. The company has said that it found 18 YouTube channels that were likely associated with Internet Research Agency. Accounts linked to the agency purchased $4,700 worth of ads. YouTube also included the Russian media outlet Russia Today, or RT, as part of its preferred lineup of YouTube channels, which are bundled and presented to advertisers as attractive outlets. Youtube has since removed RT as a preferred channel, but still permits the company, which has now registered as a foreign agent, to purchase Google ads. In its written response to questions from Congress, Google's general counsel Kent Walker wrote, "We’ve seen no evidence that they are violating these policies."

In addition to the successful hacks of the Democratic National Committee's servers and the email account of Hillary Clinton's campaign chair John Podesta, the Russians launched a simultaneous attack on the US public on social media. That much is now clear. Rather than attempting to glean information from prominent elected officials, this offensive sought to pit voters against each other by posing as activists on both sides of an issue and spreading divisive content on each side. It makes sense, then, that Mueller's investigation into Russian interference in the election would include the titans of Silicon Valley that enabled Russia's attempts to spread that hatred and chaos.

1Update: 10:55 AM EDT 1/27/18 This story was updated to provide additional comment provided by Cambridge Analytica after publication about the nature of the company's outreach to Julian Assange.

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