Anti-war protestors closed down the UK government's 10 Downing Street website for a short period over the weekend.
In a posting on the independent media site Indymedia, uk.indymedia.org, on 23 March protestors claimed to have made the site, and other government sites, temporarily inaccessible due to a denial-of-service attack (DOS).
Jason Holloway, UK general manager of Cambridge-based security firm F-Secure UK, confirmed on the site had suffered a DOS attack.
F-Secure has been tracking war-related attacks and 10 Downing Street is not alone in this: more than 20,000 sites have been attacked in the past week, Holloway said.
"We have a large database of all the places that have been hacked, either denial-of-service or they have been defaced. The vast majority [of the hackers] are anti-war but there are also anti-US and anti-Muslim [attacks]," Holloway said.
Sites such as the Electrohippie Collective's www.fraw.org.uk/ehippies/ have been encouraging such attacks, offering downloadable Java programs that will run "cyber sit-ins" from the user's computer. The Electrohippie site is specifically targeting 10 Downing Street and the US White House sites.
F-Secure has heard unconfirmed reports that the White House site has been hit by a similar attack, "but that is only from one source", Holloway said.
A Downing Street spokesman said he did not know whether or not the site had been attacked.