The Defense Department temporarily cut off public access to most of its Web sites on Monday to ensure that they are protected against the "Code Red" computer virus. Some versions of the virus display the slogan "Hacked by Chinese!" on infected Internet sites. Meanwhile, the nation's leading Internet security group issued an extraordinary warning Monday that vast numbers of home computers with high-speed Internet connections are being targeted by hackers who use them to launch potentially devastating online attacks, reports the Los Angeles Times. The CERT Coordination Center at Carnegie Mellon University pleaded for help Monday in educating computer users on the importance of practicing good computer hygiene.