Unmasked

Anonymous got lucky. When five of its hackers attacked security company HBGary Federal on February 6, 2011, they were doing so in order to defend the group’s privacy. It wasn’t because they hoped to reveal plans to attack WikiLeaks, create surveillance cells targeting pro-union organizations, and sell sophisticated rootkits to the US government for use as offensive cyber weapons—but that’s what they found.

In the weeks after the attack, the hackers released tens of thousands of e-mail messag...