TorrentFreak reports that on Saturday 4Chan's 'Anonymous' launched a DDoS attack on Aiplex Software, an anti-piracy outfit hired by the MPAA to launch DDoS attacks on torrent sites that failed to respond to copyright infringement notices sent by the MPAA. Once Aiplex went down, 4Chan moved on to bigger and better targets.
According to TorrentFreak, the assault on MPAA.org was successful; the site was taken offline within minutes and remained down for 18 hours until the MPAA moved its site to another IP address.
4Chan continued their efforts on Sunday and with the help of sympathizers, took down the RIAA website with a separate attack. The RIAA attack was scheduled for 3 p.m. Eastern Time and the site went down five minutes before that time.
Both the MPAA and Aiplex confirmed to the BBC that DDoS attacks were responsible for site downtime over the weekend.