I've got quite a few of these myself, be aware if they make it to your mailbox:

A new mass-mailing virus, which disguises itself as a file sent by a computer user's network administrator, began infecting systems Friday.
The worm, which is being dubbed "mimail," attempts to exploit a vulnerability in Internet Explorer that allows a script to be executed by an infected computer. The worm then tries to use that script to mass e-mail itself, potentially clogging mail servers or slowing down networks, according to antivirus company Symantec.

Read more: CNet News.