Know Your Digital Parasites

As the “Blaster” worm explodes across the Internet, computer security experts are reminding users to keep their machines’ protective software up-to-date. The new worm exploits a security hole that Microsoft publicized weeks ago, but thousands of machines remain vulnerable because users didn’t install the free patch. Some reports even indicate that Blaster will try to overwhelm the Microsoft server where users can download the fix. In a May “Explainer,” Brendan I. Koerner parsed out the difference between a virus and a worm.