Mastering™ Network Security, Second Edition

10.3. Worms

Traditionally, a computer worm was considered an application that could replicate itself via a permanent or a dial-up network connection. Unlike a virus, which seeds itself within the computer's hard disk or file system, a worm is a self-supporting program. A typical worm maintains only a functional copy of itself in active memory; it does not even write itself to disk.

However, in the last few years, the boundary between worms and viruses has become increasingly blurry, starting with Melissa. Melissa was a worm/virus hybrid that could infect a system (like a virus) by modifying documents to include quotes from The Simpsons television show. But it could also use the Address Book in Microsoft Outlook and Outlook Express to resend ...