The US Justice department's website was hacked following the suicide of Aaron Swartz.
Hacktivist group, Anonymous, has claimed responsibility for hacking a US government website following the death of Aaron Swartz, an American computer programmer and Internet activist.
Anonymous hacked the US Justice Department's (USSC) website and posted a video on it.
In the video, Anonymous said: "Two weeks ago today, a line was crossed. Two weeks ago today, Aaron Swartz was killed. Killed because he faced an impossible choice. Killed because he was forced into playing a game he could not win -- a twisted and distorted perversion of justice -- a game where the only winning move was not to play."
The group said federal sentencing guidelines enable prosecutors to cheat citizens of their constitutionally-guaranteed right to a fair trial.
The group also said they copied secret information from several government computer systems and made it public.
FBI executive assistant director, Richard McFeely, told Reuters the agency is investigating the attack.
"We were aware as soon as it happened and are handling it as a criminal investigation. We are always concerned when someone illegally accesses another person's or government agency's network," McFeely said.
In November 2012, Anonymous launched a series of cyber attacks against websites in Israel following its assault on Gaza.
Last year, Anonymous claimed it attacked and forced a number of UK government's websites offline in response to the country's treament of Julian Assange.