It was on Christmas Day that Facebook's Chief Security Officer Joe Sullivan first noticed strange things going on in Tunisia. Reports started to trickle in that political-protest pages were being hacked. "We were getting anecdotal reports saying, 'It looks like someone logged into my account and deleted it,'" Sullivan said. For Tunisians, it was another run-in with Ammar, the nickname they've given to the authorities that censor the country's Internet. They'd come to expect it. In the days after the holiday, Sullivan's security team started to take a closer look at the data, but it wasn't entirely clear what...