MADISON, Wis. -- We've all been trained not to open file attachments that wind up in our e-mail in box. But what if the virus can get you even when you don't open it?

For many people, this virus is much scarier than something that crashes your computer or deletes your files.

The "badtrans worm" arrives under one of many aliases and it logs every keystroke you make and sends them back to its master. The hacker can then look at everything you've typed, including credit card numbers you've shopped with.

"It also installs remote access software -- so if you were compromised by it, if you don't have other defenses in the way, the adversary, whoever it is, might be able to access your machine over the internet and control it," said Peyton Engel of Berbee, a computer company in Madison, Wis.

And it all happens without you opening the file, because older versions of Microsoft Outlook will just activate the file from that preview pane that most of us leave open.

So even if you click on the message to delete it, you've done enough to release it into your system.

Make sure your virus software is up to date, and it'll catch the virus before you even have the chance to activate it.

Download the latest fixes for Outlook. There are free patches on Microsoft's Web site to keep Badtrans from launching in that preview pane.

Once badtrans is on your system, it automatically mails itself to everybody that sends you e-mail.

Here are the basic steps for containing the worm:

Download Microsoft's Outlook Security Patch. Visit CNET to download the Microsoft Email Attachment Vulnerability Patch. Click here if you use Microsoft 5.5. Click here if you have Microsoft 5.01

Remove It From Your System. If you already have the worm, click here for a free download to detect and remove the Badtrans virus.

"Don't open attachments!" One of the best ways to prevent virus infections is not to open attachments, especially when viruses such as Badtrans are being actively circulated. Even if the e-mail is from a known source, be careful. A few viruses take the mailing lists from an infected computer and send out new messages with its destructive payload attached. Always scan the attached files first for viruses. Unless it's a file or an image you are expecting, delete it.

Stay informed. Did you know that there are virus and security alerts almost every day? Keep up-to-date on breaking viruses and solutions. One of the best sites to check is Symantec

Get protected. If you don't already have virus protection software on your machine, you should. If you're on a network, check with your network administrator first.

Scan your system regularly. If you're just loading antivirus software for the first time, it's a good idea to let it scan your entire system. It's better to start with your PC clean and free of virus problems. Often the antivirus program can be set to scan each time the computer is rebooted or on a periodic schedule. Some will scan in the background while you are connected to the Internet. Make it a regular habit to scan for viruses.

Update your antivirus software. Now that you have virus protection software installed, make sure it's up-to-date. Some antivirus protection programs have a feature that will automatically link to the Internet and add new virus detection code whenever the software vendor discovers a new threat.