Facebook has suspended the data analytics firm Cambridge Analytica over a massive data breach that allegedly targeted millions of U.S. voters.

A whistleblower charges that the Trump campaign-linked firm reaped information from the profiles of 50 million unsuspecting American Facebook users and built a software program to feed them personalized political advertising during the 2016 election campaign.

The Trump campaign on Saturday denied using the firm’s data, The Associated Press reports. “The campaign used the RNC for its voter data and not Cambridge Analytica,” the campaign said in a statement. “Using the RNC data was one of the best choices the campaign made. Any claims that voter data were used from another source to support the victory in 2016 are false.”

But The Observer reports:

Christopher Wylie, who worked with a Cambridge University academic to obtain the data, told the Observer: “We exploited Facebook to harvest millions of people’s profiles. And built models to exploit what we knew about them and target their inner demons. That was the basis the entire company was built on.” Documents seen by the Observer, and confirmed by a Facebook statement, show that by late 2015 the company had found out that information had been harvested on an unprecedented scale. However, at the time it failed to alert users and took only limited steps to recover and secure the private information of more than 50 million individuals.

The New York Times has the inside story:

As the upstart voter-profiling company Cambridge Analytica prepared to wade into the 2014 American midterm elections, it had a problem. The firm had secured a $15 million investment from Robert Mercer, the wealthy Republican donor, and wooed his political adviser, Stephen K. Bannon, with the promise of tools that could identify the personalities of American voters and influence their behavior. But it did not have the data to make its new products work. So the firm harvested private information from the Facebook profiles of more than 50 million users without their permission, according to former Cambridge employees, associates and documents, making it one of the largest data leaks in the social network’s history. The breach allowed the company to exploit the private social media activity of a huge swath of the American electorate, developing techniques that underpinned its work on President Trump’s campaign in 2016.

In December, special counsel Robert Mueller, who is investigating Russia’s role in the 2016 election, asked Cambridge Analytica to turn over documents concerning the campaign.

The Associated Press adds: “Britain’s information commissioner is investigating whether Facebook data was “illegally acquired and used.”

—Posted by Gregory Glover