The organization that usually warns others when hackers and crackers are at work is under attack itself.

The Computer Emergency Response Team, CERT, has been fighting to keep its Web site online in the face of a denial-of-service attack.

Since Tuesday, the site has been bombarded by a flood of bogus data requests. The FBI says these types of attacks will likely become more common. A recent study found more than 4,000 a week are being launched.

Endless stream of requests

The servers hosting CERT's Web site are being flooded with false data requests from machines around the Web. These computers have been invaded by malicious hackers who implanted a program set to fire off the data requests.

When servers are bombarded, legitimate users have trouble accessing the Web site, or may not be able to get to it at all.

Often, it's difficult to figure out where the attacks are coming from, because the requests contain false addresses.

Careful planning

Internet security experts say the CERT attack looks well planned and carefully carried out - especially since it was able to shut down the site for so long. They say typically, Web servers recover or stop a denial-of-service attack after a few hours.

As a centre of excellence in Web security, the CERT lab is a common target for crackers looking to prove their skill.

A notice on the site reads: "The CERT/CC has been experiencing a distributed-denial-of-service (DDoS) attack. The CERT web site may be unavailable at times, or performance may be reduced."