Virgin Media was forced to take its website offline for an hour yesterday during a hack attack.
It is thought the action was perpetrated by the censorship group Anonymous in response to Virgin Media's decision to block popular filesharing website The Pirate Bay.
Following a High Court order last week, Virgin Media became the first broadband provider to block its customers from accessing the site.
The ruling stated that The Pirate Bay enables breaches of copyright laws.
Twitter accounts associated with Anonymous, which regards the ruling as censorship, announced: "Virgin Media - Tango Down #OpTPB".
Virgin Media took its website down at about 17:00 yesterday.
In a statement the company said: "Our website has been the subject of denial of service attacks so we've taken the site offline for a short period of time."
The Pirate Bay also condemned the Anonymous action on its Facebook page.
"We do NOT encourage these actions," it said. "We believe in the open and free internets, where anyone can express their views. Even if we strongly disagree with them and even if they hate us."