Welcome aboard, techgrrl!
BTW, technically, Zotob is a "worm", not a "virus".
A virus is distributed via a launching mechanism, like as an infected email attachment or image file, and depends on the target user taking some action, like opening the attachment or viewing the image.
A worm does not need any help. Zotob, like other worms, simply spreads itself using information about its host's network address. Zotob, in particular, installs a little independent FTP server and then sends and receives its compatriot nasty program files by reaching out to other IP addresses within the "B-class" block (255.255.0.0) that the host address is using. When it finds a vulnerable system within those addresses, it installs its FTP program and keeps going.
Zotob reaches out beyond the B-class network using IRC channels.
As a quick helper, for those of you who are affected, one of your problems is that you can no longer connect to Symantec or McAfee or Microsoft or Sophos or any other well-known anti-virus site so you can download a patch. This is one of the things Zotob does, but it's easy to get around, at least until you reboot.
If infected with Zotob, go into your Windows directory and look for a file named simply "hosts". If you open hosts in a text editor, you will see a whole bunch of entries for various anti-virus companies in there, all followed by the IP address "127.0.0.1". Since Windows looks to the hosts file to help it figure out which special domain resolves to which IP address, the hosts file (as modified by Zotob) is basically telling your computer that all roads to anti-virus websites lead back to your computer.
Delete all of the entries in hosts (Select->All ... Delete), save the file (there's no file extension) and launch your web browser to download your patch from your favorite anti-virus site. Once installed, DISCONNECT the cable that connects you to your ISP to keep Zotob from spreading while you kill it. Run a deep scan on your system to clean out the Zotob nasty files and kill the processes it is using to spread itself.
Then (right away) go to Windows Update and install the three security patches that will keep Zotob from reinfecting your system.
Have fun! (Go Linux!)
More info on Zotob-A from F-Secure
Oops! More fun ... Today (Aug.18) Microsoft is investigating ANOTHER critical flaw in its browser (demonstrated with MSIE6 and a fully-patched Windows XP SP2 system). While you're downloading the Zotob security patches, be sure to pick up the new patch MS will be making available to thwart this new hack. If it's not up there, yet, go back to Windows Update every few hours to look for it and install it. It seems this exploit is targeted at machines with MS Visual Studio installed, however some of the target files are also included with Windows XP SP2. Read more ...