Here are 5 things to know about the alleged Facebook data leak:
London-based Cambridge Analytica received user data from a Facebook app years ago that purported to be a psychological research tool, though the firm was not authorised to have that information.
Mr Trump's campaign reportedly used the firm's data during the primary elections but not during the general polls and Federal Election Commission numbers showed that the firm collected $5.9 million in 2016 from Mr Trump's campaign.
However, Cambridge Analytica has denied media reports that it misused data, and said that it deleted all Facebook data obtained from a third-party application in 2014 after learning the information did not adhere to data protection rules.
Facebook said it was pressing Cambridge Analytica for answers, after getting assurances from the firm in 2015 that it had deleted all data. Facebook has hired forensic auditors from the firm Stroz Friedberg to help, according to a report by Reuters.
Facebook's Chief Information Security Officer Alex Stamos, is planning to leave the company by August, according to IANS, after this alleged data breach. (With Agency Inputs)