Hackers retaliate over Megaupload website shutdown
20 January 2012 Last updated at 11:06 GMT
Hackers have targeted the US government and copyright organisations following the shutdown of the Megaupload file-sharing website.
The Department of Justice (DoJ), FBI and the Motion Picture Association of America (MPAA) among others have been bombarded with internet traffic.
Web links have been been distributed which, when clicked, make the user's computer part of the attack.
A statement attributed to Anonymous claimed responsibility.
Rory Cellan-Jones reports.