Computer security researchers said have said that an unprecedented mass cyber protest was triggered by efforts by film and music trade groups to close online piracy haunts.

Members of 4chan online forum that promotes users remaining anonymous organised distributed denial-of-service (DDoS) attacks on websites for the Recording Industry Association of America (RIAA) and the Motion Picture Association of America (MPAA), according to the security firm PandaLabs.

DDoS attacks are efforts to overload websites with so many simultaneous requests that computer servers can't handle the load and freeze or crash.

Attacks on RIAA caused a dozens of interruptions in service, taking down the group's website for a total of one hour and 37 minutes, according to PandaLabs.

Protest organisers gave instructions throughout the weekend at 4chan, providing the online computer address and when to strike, the researchers reported .

"The most significant aspect of this event, in addition to the damage caused, is that it could mark the first mass cyber protest of its kind on the Web," PandaLabs technical director Luis Corrons said yesterday.

"This attack is an example of the potential for future cyber protests and the difficulty in pinpointing and stopping them."

A DDoS attack was also launched on an Indian software company hired by RIAA and MPAA to shut down free file-sharing sites such as The Pirate Bay, which the trade groups argue are haunts for swapping pirated films and music.