No one but Hector Xavier Monsegur can know why or when he became Sabu, joining the strange and chaotic Internet collective known as Anonymous. But we know the moment he gave Sabu up. On June 7, 2011, federal agents came to his apartment on New York’s Lower East Side and threatened the 28-year-old with an array of charges that could add up to 124 years in prison. So Hector Monsegur, who as Sabu had become a mentor and icon to fellow members of Anonymous, surrendered his online identity to a new, equally faceless and secretive master: the FBI.