Microsoft Warns Internet Explorer Users About Worm

A security bulletin on the company's Web site says Microsoft started investigating a "mass mailer worm," dubbed W32/Mimail(at)MM, late Friday morning.

The worm spreads through e-mail if recipients open an attached zip file--used to condense information so it can move faster over the Internet--then open an HTML file inside the zip file, the bulletin said.

The worm exploits a vulnerability the company addressed in a security bulletin issued April 23, the bulletin said.

On Saturday, Microsoft spokesman Sean Sundwall downplayed the worm's potential to cause major security problems.

If someone opens the e-mail, the zip file and the HTML file, the virus is sent to all e-mail addresses the worm finds on that computer, Sundwall said.

"The damage is simply an annoying e-mail," Sundwall said.

Microsoft's Web site directs customers to a security patch designed to fix the problem.