Surfers were intermittently unable to reach the websites of the Japanese prime minister and Cabinet Office this week following a sustained denial of service attack. Japan Today reports the National Police Agency is tracing the source of attacks which left Japanese government websites difficult to reach between Tuesday and Wednesday this week (22 and 23 February). Meanwhile officials are reviewing security.

"We had rather significant attacks," Chief Cabinet Secretary Hiroyuki Hosoda told a news conference, AP reports. "We must thoroughly check risk control measures not only at the Prime Minister's Office but other government offices as well."

The source and motive of the attacks - which caused no permanent damage - remains unclear. Normal service has been restored but the fact that the latest assaults follow similar strikes in January and August 2004, which also caused little damage, raises concerns that further assaults might follow.

Distributed denial of service attacks have become a huge issue for internet businesses over recent months as crackers have taken advantage of networks of compromised PCs to flood sites with useless traffic, leaving them unable to service legitimate requests. Bookmakers, internet payment firms, IT suppliers and government agencies have all become the target of attacks which can prove difficult to thwart. ®

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