] A new e-mail worm that first appeared on the Internet this
] afternoon is spreading rapidly, according to leading security
] companies.
 . . .
] The worm arrives as an e-mail with an attachment that can have
] various names and extensions. The message can have a variety of
] subject lines and body texts, but in many cases it will appear
] to be an error report stating that the message body can't be
] displayed and has instead been attached in a file.

Computerworld: New 'Mydoom' worm spreading faster than last year's Sobig-F