Facebook fired 52 people for accessing user data for personal reasons between January 2014 and August 2015 and directly helped former US President Donald Trump amplify his rhetoric, according to a new book.
An Ugly Truth: Inside Facebook's Battle for Domination by journalists Sheera Frenkel and Cecilia Kang, details how one engineer used user data to "confront" a woman who he had been holidaying with but had left him after a row.
Business Insider reports another engineer at the company used his access to find information on a woman he had gone on a date with but had subsequently stopped responding to his messages.
The woman had the Facebook app installed on her phone, meaning he was able to see real-time location details.
The book's authors wrote that most of those who took advantage of the access were men "who looked up the Facebook profiles of women they were interested in", adding there was "nothing but the goodwill of the employees themselves to stop them from abusing their access to users' private information."
Facebook fires anyone who is found to have accessed user data for non-business purposes, the company said.
"We've always had zero tolerance for abuse and have fired every single employee ever found to be improperly accessing data," a Facebook spokesperson told Insider via statement.
"Since 2015, we've continued to strengthen our employee training, abuse detection, and prevention protocols. We're also continuing to reduce the need for engineers to access some types of data as they work to build and support our services."
The book says that 16,000 employees had access to users' private data in 2015.
In an interview with NPR, Frenkel also confirmed that Facebook employees were embedded with Donald Trump's Presidential campaign against Hillary Clinton.
"So interestingly, this is something Facebook actually offered both campaigns. The Hillary Clinton campaign just turned them down and said that they didn't want that kind of assistance," she said.
"The Trump campaign ended up with Facebook employees in their offices advising them on how to best use Facebook tools. And that trove of data was so important to the Trump campaign in understanding who their voters were."
The advice also included helping the former US President's campaign to amplify all content, regardless of whether it was misinformation, conspiracies or false information.
"Often they don't even look at the content themselves. They just give them the data. This messaging is working and that messaging is not," Frenkel said.
The book also deals with Russia's interference in the 2016 US Presidential election.