For the past 2 days, an ugly virus named ExploreZip has been destroying the contents of hard drives all over the world. The virus comes to you as a response to email you send to an infected system. It's an auto-response to your message, and it uses the same text in the subject line that you used when you sent your own message. This, of course, makes the message look safe. The message body looks like this:
Hi
Boot to MS-DOS
Delete \Windows\System\Explore.exe
Edit Win.ini to remove the line "Run=c:\Windows\System\Explore.exe
For Windows NT
Delete \Windows\System\Explore.exe
Run REGEDIT (do not use REGEDT32) and go to HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows and remove the key named "Run=C:\Windows\System\Explore.exe.
If you run Exchange Server, use your virus detection software for Exchange Server to clean up the server (if you don't have one, McAfee has a VirusScan program that runs at the command line, and other vendors probably offer Exchange Server virus protection too).
Although the antivirus program removes the infection from current email attachments, previously infected email messages will be sent to recipients. However, the virus attachment has a size of zero bytes and is disabled. You might want to send email to recipients (or call them) to apprise them of that fact. Be sure to stress the fact that they should delete the attachment anyway.