Facebook CEO Mark Zuckerberg is testifying on Capitol Hill to answer questions about protecting user data. The Tuesday hearing held by the Senate Judiciary and Commerce committees follows news that the data-mining and political consulting firm Cambridge Analytica obtained personal information of up to 87 million Facebook users. The firm is accused of using that information to target Facebook users with political advertising in 2016. The two Senate committees are holding a joint hearing called "Facebook, Social Media Privacy, and the Use and Abuse of Data." It is expected to start around 2:15 p.m. on Tuesday.