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Computerworld - Web site administrators are being advised by the FBI's cybercrime division to be especially vigilant in looking for evidence of distributed

Service Denied How DDOS attacks work: Hackers overload targeted computer networks by smothering them with reams of data. The overloads cause the networks to slow and eventually stop responding. At present, there are no sure ways to halt DDOS attacks.

denial-of-service (DDOS) attacks that have recently hit Web sites.
In an advisory issued last week by the FBI's National Infrastructure Protection Center (NIPC), the agency said it has received information about "ongoing attempts to disrupt Web access to several sites."
The NIPC advisory came after a DDOS attack on the White House Web site on May 4. That attack lasted from about 8 to 11:15 a.m. EDT, causing so many automated requests for information that the servers were overloaded.
An NIPC spokeswoman declined to elaborate on the advisory.
Last week's notice followed an NIPC warning last month of an expected upswing in attacks by Chinese hackers against U.S. servers as a result of an increase in political tensions between the two countries.
The latest attacks cited by the NIPC have been seen on several networks, using data fragmented into large User Datagram Protocol (UDP) packets for transmission. The packets are directed at the commonly used Port 80.
The attackers are apparently using this method to try to bypass standard port protocol blocking techniques, according to the NIPC.
To detect such attacks, network administrators should inspect firewall logs and other records for evidence of fragmented UDP packets directed at Port 80. Such inbound packets indicate that a denial of service to the network may be under way. Outbound UDP packets indicate that there's a high likelihood that the network is already compromised by hacker DDOS software.
A special utility to detect DDOS software is available from the NIPC at www.nipc.gov/warnings/advisories/2000/00-055.htm.
Ric Steinberger, technology director at San Francisco-based AtomicTangerine Inc., formerly known as SecurityPortal.com, said such attacks have been common for years. Steinberger said he believes the NIPC issued this latest advisory in direct response to the DDOS attack on the White House Web site. "The NIPC needs to issue alerts when one or more federal Web sites have been attacked in this way," he said.
Most private business sites probably have Web servers equipped with firewalls that can help thwart these types of attacks, said Steinberger. Government sites, however, are usually more vulnerable because their staffs aren't as highly paid as their private-sector counterparts and don't have access to the most current software and hardware defenses,he said.

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