Computer viruses most commonly are spread through email, reports the United States Computer Emergency Readiness Team (US-CERT.) US-CERT defines a computer virus as "a program that spreads by first infecting files or the system areas of a computer or network router's hard drive and then making copies of itself." Computer viruses can destroy files, cause programs to malfunction and cause other damage within the computer.
Basics of an email virus
A computer virus typically needs a user action to activate it. Often this action occurs when you open a new Web page or email attachment. Depending upon how your email program is configured, a virus may become activated simply when you open an email message. The email message is opened and the virus is released into the computer.
Reasons why opening an email can activate a virus
Opening an email seems like a harmless action. However, unscrupulous people release viruses to multitudes of computers through email messages. This occurs more often when your email settings allow HTML or HyperText Markup Language. HTML is the type of computer language used for creating Web pages or other items that may be found via a Web browser. Set your email to display messages only in plain text to reduce the chance of activating an email virus.
If your email program has a preview window (Outlook and Outlook Express both do), disable the preview option. Some computer viruses are activated as soon as the preview window for the email message is launched. The virus activates within the preview window before the actual message is even opened.
Attachments sent through emails are often the delivery system for viruses. Disable any auto-open for attachments feature your email program may have. In addition, never open any attachments from people you do not know. Even if the attachment is from someone you know, be wary. Sometimes email from friends or coworkers may have been hijacked by a virus and they may not know they are sending harmful attachments to you.
Preventing email viruses
Antivirus software can be one of the best ways to prevent email viruses. Utilize the security features your email program offers and never turn off the standard virus detection protection. Be sure to initiate antivirus updates. Once a week, run your computer's antivirus program. It will scan all the files and data and check for viruses and other potentially harmful things such as Trojan Horses and malware. If a virus or other problem is detected, follow all instructions on how to remove it from your computer.
Antivirus programs such as Norton, Kaspersky and McAfee can run in the background of your computer while you read and send email or run an Internet browser, opening and engaging on Web pages. You can set antivirus programs to run quick scans each time you turn on your computer or even set it to run each time you open your email program.
Another way to prevent email viruses is education. Keep informed about potential computer virus threats via news programs or by subscribing to US-CERT's National Cyber Awareness System.