Updated: The US Sentencing Commission website has now been restored.
Early Saturday morning, members of Anonymous claimed to have brought down ussc.gov, the website for the United Stated Sentencing Commission, an independent arm of the federal judicial branch responsible for setting sentencing guidelines. ZDNet reports that the site was replaced with a message from Anonymous citing the death of Aaron Swartz as the motivation for the attack. The website has since been taken offline. Anonymous also claimed to have pilfered information about the Supreme Court Justices, although the nature of that information—and the accuracy of that claim—remains unknown.
According to Bloomberg, Richard McFeely, executive assistant director of the FBI's Criminal, Cyber, Response, and Services Branch, responded with a statement Saturday morning: "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."