User ManualEmail Discussion Group User Guide GlossaryComputer Malware and Zombie Computers

Computer Malware and Zombie Computers

It is possible for some types of email to carry computer malware to your subscribers. If you run your discussion group with the default settings, that will never happen at

What does malware do?

A virus computer program or malware can damage your personal computer, by deleting or corrupting files on your hard disk.  It can also silently intercept your keystrokes, and capture the passwords to your online bank accounts.  Other variations of these destructive programs are called trojan horses and worms.


Computer malware will allow somebody else to remotely control the computer.  The owner of the computer is rarely aware of the problem, and thus these computers are called zombies.  It is estimated that millions of Windows computers in the United States have been taken over and are secretly under the control of somebody else.  Among other problems, this is a big national security risk.

Currently, the most common action taken is to send out spam, especially to email addresses of contacts found on your computer.  Some of the emails contain the same trojan horse as an attachment, thus spreading the problem.

Attachments and HTML can carry malware

Computer malware can be spread via attachments.  We have had viruses in PDF's, MS Word Documents, executable programs, Flash videos, pictures, music, and about any other file type you can think of.  The computer virus scanners currently know about more than 1 million different computer viruses.  Although, the number of viruses found actively circulating is much smaller.

Computer malware can be spread in HTML email, because HTML has a feature that allows small programs to be downloaded and run on your computer.  Java, Javascript and VBscript are examples of these types of languages.  When you see rotating graphics, pop-up windows, and other fancy web page effects, it is typically small programs written in these languages that are doing the work.  If the program was malware instead, bad things would happen to your computer.

HTML email can also allow linking to websites that contain the malware.  The program was not downloaded inside the email, but brought in from the remote server.  This type of malware is called cross-site scripting.

Plain Text Emails can save the world!

The only good news is that plain text email cannot be used, and never has been, to send a computer virus.  All of the email sent through has been converted to plain text email.  We never send out HTML email. If your subscribers send messages in HTML email, it is first converted to plain text before being sent to your list.

By default, will remove any attachments sent to your announcement list.  So, if you run your Discussion Group in the default mode, then there is no chance that any email to your list will ever affect your subscribers.

If you choose to allow attachments to your list, our system will scan these attachments with two different virus scanners, Clam-AV and Sophos.  Therefore, even with attachments, there is a low risk of bad things happening to your subscriber's computer.

Attachments as clickable links

If you manage an email discussion group, please review the information below to allow attachments and clickable links:

If you manage an announcement list, please review the information below for using clickable links:

More Resources:

For additional information, here are some links to web resources