Quite a few of these worms will send themselves to everyone on your e-mail list, and thus attempt to spread themselves. It's a fairly common problem, as the virus/worm often exploits flaws in Microsoft software which, as you know, is also quite common. Some will also infect computers using other e-mail programs and operating systems as well. You're already doing the right thing by using an anti-virus program (be sure to keep this updated)and by being careful about what e-mails you open. If you're using Windows, it's also a good idea to check the Windows Update website for any fixes they might have to offer. It doesn't have much to do with viruses/worms, but www.grc.com has some useful information on making computers that use Windows less vulnerable to intrusions, such as a means of closing ports that Windows leaves open by default. If you're connected through a cable modem or use a system that is otherwise always connected to the net, I'd suggest a firewall such as Zone Alarm. If you happen to be running a Linux box, I can direct you to some very good Linux security information; just let me know.