U.S. antivirus software vendor Network Associates Inc. (NAI) was hit by a DoS (denial-of-service) attack late Wednesday, a company executive confirmed Thursday. Access to NAI's Web site was hampered for a period of about 90 minutes, although the site never went fully offline, according to Jim Magdych, security research manager at the Computer Vulnerability Emergency Response Team (COVERT) at PGP Security, an NAI business.

Some users were unable to connect to the NAI Web site during the attack, while others could access the site but experienced slow responses to their queries, Magdych said. All NAI's sites worldwide were affected.

DoS attacks can disable a Web server or other type of computer by bombarding it with a high volume of fake requests for information, causing the target computer to crash or become so overwhelmed that it grinds to a halt. Just last week, Microsoft Corp. was hit with two DoS attacks, one of which disabled most of its popular Web destinations for several hours. NAI's IT department is still trying to identify the source of the attack, Magdych said. He declined to comment on whether NAI would call in the U.S. Federal Bureau of Investigation (FBI). Microsoft has already asked the FBI to investigate its DoS attacks.

The DoS attack was against NAI's DNS (domain name system) server, not its Web servers, Magdych said. However, the attack didn't "exploit the vulnerabilities" COVERT documented on Monday, he added. "It was a simple flooding attack," Magdych said.

COVERT on Monday warned of vulnerabilities in the software used in most DNS servers. At that time, Magdych said that flaws in two widely used versions of BIND (Berkeley Internet Name Domain), distributed free by the Internet Software Consortium (ISC), could be exploited immediately by unscrupulous programmers.

If exploited, the vulnerabilities could enable hackers to shut down both ISPs (Internet service providers) and corporate Web servers as well as steal data. COVERT and ISC posted patches for the vulnerability at http://www.isc.org/. Given the publicity COVERT's announcement gained, Magdych said hackers' ire against NAI may be behind the DoS attack. "It certainly could be a motivating factor," he said.

Simple flooding DoS attacks are very hard to counter since all servers have physical limits of how much traffic they can handle, Magdych said. He added that NAI's IT department has already implemented the necessary means to try and minimize any future such attacks.

NAI's IT department noticed the DoS attack immediately since it "proactively monitors anomalous traffic," Magdych said. Within 15 minutes of the attack beginning, the IT department had assembled a team to deal with the problem and was in contact with NAI's ISP.

Network Associates, in Santa Clara, California, can be reached at +1-408-988-3832 or at http://www.nai.com/.