In January, the hacker group Anonymous staged a demonstration at a BART station in San Francisco after officials turned off cell phone service in its stations. Justin Sullivan/Getty Images hide caption
Anonymous Anonymous
The Greek Ministry of Justice website after it was hacked earlier today. Louisa Gouliamaki /AFP/Getty Images hide caption
The Guy Fawkes mask has come to symbolize the group Anonymous. This mask was seen during protest in Germany. Sean Gallup/Getty Images hide caption