Chinese hackers may step up attacks against U.S.-based government and company networks and Web sites, warns the National Infrastructure Protection Center. According to the announcement, companies should be on the lookout for attacks stemming from politically motivated Chinese hackers from April 30 through May 7.

Security analysts say there's some evidence that Chinese hackers began attacking the United States after the midair collision of a U.S. intelligence plane and a Chinese fighter. The NIPC says hackers have defaced a number of U.S. sites with anti-U.S. or pro-Chinese rhetoric. The organization also repeated an earlier warning about "Lion," an Internet worm that's infecting systems with distributed denial-of-service attack tools. When exploited, the worm's source code allegedly sends passwords to an E-mail address in China.

Hurwitz Group security analyst Pete Lindstrom says companies need not panic over these warnings, but companies closely affiliated with the U.S. government may be targeted. "It is a safe assumption to make that China and the U.S. are exercising their cybermuscles against one another," he says. According to the Web site Attrition.org, hacks against Chinese sites have skyrocketed in recent weeks. There's no way to confirm exactly where those attacks are originating, but many contain pro-U.S. rhetoric.

The U.S. government asks that any attacks or intrusions be reported to the FBI at www.fbi.gov/contact/fo/fo.htm or to the NIPC.

--George V. Hulme