Keeping viruses at bay: with new internet viruses more insidious than ever; here's how districts can fight back.

A few years ago, a high school student from Michigan was expelled for intentionally downloading viruses from the Internet to a home computer and unleashing them in his school's computer lab. The viruses disrupted computer use throughout the district by preventing infected machines from booting, and the school network had to be shut down to check 800 PCs and clean up 130 contaminated systems. At the time, the school was not running anti-virus software because of budget constraints, and the false savings resulted in estimated damages exceeding $60,000.

More than 70,000 computer viruses have now been identified with potential to destroy operating systems, erase files and reformat hard drives. New examples are discovered daily. But since most viruses are contracted directly and inadvertently through the Internet, protecting school computers as your students and staff use online resources is deadly serious business.

DANGEROUS NEW BREEDS Dangerous new viruses have now been developed with the capacity to send copies of themselves to random e-mail addresses on infected machines, so the situation is worse than ever. Your school and personal computers are therefore vulnerable to viruses attached to bogus e-mail sent from administrators, teachers and education company representatives without their knowledge. I receive two to five such messages daily.

Although it is not possible to get viruses simply by reading e-mail, unless the infected attachments are opened, the viruses are insidious in tricking recipients to do just that. Examples include CodeRed and Nimda--"admin" spelled backwards--that launched 1.2 million attacks the day after hitting the Internet a year ago, and Klez, which tops the current lists.

THE NOTORIOUS KLEZ Klez generates e-mail with captivating subject lines such as "A special new game," "How are you?" and "Returned mail," with message come-ons such as "meeting notice," "I send this file for your advice," or "I expect that you would enjoy this." It also searches hard drives for e-mail addresses that it pirates as "return addresses" that make the messages appear legitimate.

Viruses can therefore arrive in school mailboxes attached to believable messages from people you know, as well as people you do not know. Some ironically even masquerade as free protection tools, such as "You only need to run this tool once, and then Klez will never come into your PC!" But if you are fooled into clicking on an infected attachment, your system will be trashed.

The online security firm MessageLabs (www.messagelabs. com) estimates that one in every 200 e-mail messages now carries a Klez version. It has become a major technology problem for schools. "in the last six days I caught 1,099 Klez viruses trying to enter my system," says one district technology coordinator. Another adds: "I can count on at least 10 infected attachments each day, and they seem to keep coming and coming."

BEYOND SOFTWARE SOLUTIONS The first line of defense is anti-virus software from companies such as Symantec (www.symantec.com) and McAfee (www.mcafee.com). The second line of defense is updating that protection weekly. Since some viruses can still slip by those barriers--my system catches less than half-trusting software solutions alone leads to false security. It is therefore advisable to delete suspect messages immediately--especially attachments with .bat, .exe, .pif, and .scr extensions--and scan attachments for viruses before they are opened. Since certain viruses also exploit vulnerabilities in operating systems, browsers, e-mail programs and firewalls, it is also crucial that those are updated, and the latest security patches are installed.

For more information, see the Computer Incident Advisory Capability (www.ciac.org), the Virus Encyclopedia (www.virusdatabase.com) and the Wildlist (www.wildlist.org).

Odvard Egil Dyrli, [e-mail], is senior editor and emeritus .professor of education at the University of Connecticut.