This worm disguises itself by arriving as a zip file which most scanning programs allow. A zip file is usually a method of condensing information so it can move faster over the Internet.
If a user clicks on the attachment, the worm is launched and creates a mass-mailing of itself, which may clog mail servers or degrade network performance.
Once the problem was identified, corporate computer administrators began blocking e-mails that contained the "message.zip" attachment.
As of Friday night Microsoft had not yet posted a patch, or a fix, for the problem.
