happy99

happy99 is a worm (similar to a virus) that infects computers and propagates to other computers by sending itself as email .  If you receive it by email and you open the attachment, your system becomes infected.  Then,when you send email to someone, the happy99 worm sends itself to the same address.  Your correspondent get mail from you with the worm without you even knowing you sent the mail.

For more information on this worm, including how to rid your system of it, see

 http://www.pspl.com/faqs/happyfaq.htm  

If the author of this worm had been malicious, it could easily have wiped out everything on your hard disk, or it could have searched your system for valuable information and emailed that to the author.   Fortunately, this worm does no actual damage to your system.  It's only purpose seems to be to propagate to as many systems as it can.

Because this worm propagates by sending itself as email "from" the user of the infected system, people who receive the worm see it as having been sent to them by someone they know.  This makes it all the more likely that they will open the attachment and wind up with an infected system.

The next author of such a worm may be out to see how many computers he (or she) can damage, rather than just how many he can infect.  Your only protection is never to open any email attachments.  If "never" is too strong for your style, then at least make sure you have independent verification of where the mail came from and that the person who sent it knows what it is and sent it on purpose.