Combatting Viruses
What is an email virus?
An email, or computer, virus is an executable file (typically distributed as an attachment in an email message) that can cause harm to your computer if opened. One should never open an unsolicited email attachment if they are unsure of the sender's identity. Viruses typically are not found in the body of an email message. They also do not simply float around the Internet. Viruses and other system-destroying software can only exist in executable form (e.g. *.exe, *.bat), and cannot cause harm until they are executed.
While simply reading email, you are not executing any malicious code, thus the virus cannot do damage. However, if you or your computer automatically download the files attached to an email and run them, there is a chance that files containing viruses could damage your computer. So, it is important that you do not allow your email program to automatically execute an attached file. You run a much greater of risk infection if so.
Viruses are generally operating system-specific. Viruses created for a Windows computer cannot damage a Macintosh, and vice-versa. In the future, we may see more viruses cross these boundaries as programming languages break OS-specific rules.
Where do email viruses come from?
Email viruses originate from malicious people who would like to destroy, damage, or take advantage of computer systems or their owner's personal information. These individuals accomplish this by sending viruses in Bulk Email, or Spam (not to be confused with Unsolicited Commercial Email). If you ever receive an email virus, your email address (along with thousands of others) was probably selected from the computer of an already-infected user. Viruses find possible recipients by scanning hard drives for "email-like" addresses. They look in .html, text, Windows Address Books. Some addresses may be chosen randomly by a web-crawler.
One of the current virus-sending techniques is to forge the From: field, or header, to look like the message comes from someone it does not. The reason they forge the email headers is they hope to fool email filters, confuse the recipient or obscure their identity. It is quite easy to forge the From: header. This is why you cannot always trust email on the basis of looking at whom it is from, and the infected party is difficult to discern, causing much confusion along the way.
Are viruses spread other than by email?
You can get a virus only by downloading and executing a file which is infected. There are many ways (in addition to email attachments) this can happen:
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If you download an infected file from the Internet or a website and execute it.
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If your computer is on a network, and not updated with the latest operating system patches, viruses can be transmitted directly using OS vulnerabilities and other processes (e.g. messenger services).
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If you use someone else's removable media (i.e. CD-R) without scanning it for viruses it first, or if you were to boot a computer with infected media (boot virus).
What you CAN do
- Keep your operating system (OS) updated as often as possible. Most vendors provide free, online updates to their OS. For example, Windows users should visit the Microsoft web site as often as possible to keep their computers updated and protected from vulnerabilities: http://update.microsoft.com/. Linux and Mac OS users should also make sure to keep up with the most recent patches by visiting their vendor's web site.
- CAEN strongly recommends that all users install VirusScan on their computers, and make sure it is updated daily. For more information about VirusScan, including links to download the installer, refer to the U-M Virus Busters at: http://virusbusters.itcs.umich.edu/
- If you ever receive an email that you do not recognize, especially if it contains an attachment, your best course of action is to just delete it.
- Many viruses come with standardized subjects, tempting you to open them (e.g. You win! or Your Password!). Your email program may have the ability to filter, and designing filters wisely may save a lot of time.
- If your computer is on a network, make sure you have security steps in place to prevent unauthorized users from putting files on your computer. Networks are ideal virus transmitters since there usually is a great deal of interaction between computers.
- Always run CDs or other removable media through an anti-virus program before using them, and be extremely cautious when booting your computer from rewritable media.
- Keep your email program updated! Software companies are always finding problems with their software and will post patches to update your email software. Continually check your software company's website for updates to your email program.
What NOT to do
- Do not reply to the sender. This will more than likely return your email back to your inbox as Address unknown, but could also spread the virus to others (e.g. the forged address).
- If you ever receive an email that you do not recognize, especially if it contains an attachment, do not open it! Your best course of action is to just delete it, and forget about it.
- Never download and/or run an attached file in an email from a stranger or unknown address. Be very cautious when downloading/running attachments from friends (most likely if they passed you a virus, they won't know they did!).
- Never have your email program set to run attached files automatically. This is especially true for browsers and/or email programs which automatically execute Microsoft Word after opening an email.
- Never run an executable file you have just received without first running it through an updated anti-virus utility.
Where can I find more help with email viruses?
Virus Busters provides a comprehensive approach to computer virus management. Check the their page for up-to-date anti-virus software, and if you need further help with any and all virus questions/problems:
Also, listed below are links to useful sites providing more information on email viruses:
