New virus masking as "Microsoft Internet Update Pack"
The virus which has been named W32.Swen has been in heavy circulation since Sept 17th. Swen is basically an enhanced version of the W32.Gibe virus which began circulating last year. Swen displays a very official looking screen which tells you that unless you provide your mail server name, username and password - you may lose POP3 (incoming email) functionaliy in Outlook and Outlook Express.
Swen records the information you provide, which gives the virus creators a very large list of email accounts they can use for anything they desire. Armed with a valid server name, username and password this gives them the ability to send and receive mail using your account. Not good.
The virus can spread through email, across a local network, through the Kazaa file sharing network, IRC (Internet Relay Chat) chat rooms, and USENET newsgroups.
Make sure your antivirus program is up to date, and while you are at it make a trip by Windows Update for the latest round of security patches - better safe then sorry.