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What Is A Virus?

A computer virus is a program that infects your computer and then spreads itself quickly. Viruses can often be quite difficult to eradicate. They can infect almost any type of file and then spread to other files on your computer and replicate by emailing themselves to other computers (usually by using your address book to do so). Viruses can cause varying degrees of damage depending on what the author of the virus intended. Some may only display messages or images on your screen, they can also destroy files, reformat your hard drive, or even cause your computer to no longer be able to boot up. Other viruses even downgrade the overall performance of your computer by taking up hard drive space, memory, etc.

In the past, most viruses were spread primarily via floppy disk. In the Internet age, however, most viruses spread through email. They now have the power to infect entire companies or communities in a matter of minutes. With a few hundred new viruses being detected every month, there is little chance that they will go away any time soon.

What Can You Do To Protect Yourself From Viruses?

The first step is to get an anti-virus program installed on your computer. The next step is to be cautious about each and every file or email attachment you receive, even if it's from your own family!


1) Do not open any email attachments from any source (even friends and family) without first checking them for viruses.

2) Do not open any files downloaded from the Internet without first checking them for viruses.

3) Never read, forward or reply to any chain emails, email petitions or junk email. Spam note: Do not reply to an email from and unknown source which says 'reply with the word "unsubscribe" in the Subject or message body.' It will usually have the exact opposite effect! You will end up receiving even more junk mail.

4) Update your anti-virus software regularly (minimum once a month). A few hundred viruses are discovered each month. Most anti-virus programs offer updated virus signitures or virus definitions weekly.

5) Prepare for the worst: backup your important data on a regular basis. There are many possible ways to backup your software: writable CDs, Zip disks, floppy disk, online backup sites, etc.

6) Sign up for an anti-virus email alert program. You will received notices when new viruses are found. (See Links below.)

7) Check the McAfee Anti-Virus calendar to see what viruses are "on their way."

Test Your Anti-Virus Software

It is a good idea to make sure your anti-virus software was installed properly and is working as it should. Click here to use Command Software Systems anti-virus software test.

Social Engineering

Many e-mail worms and viruses try to trick you into opening an infected e-mail attachment. Such trickery is called "Social Engineering" by hackers. All of the e-mail messages below were infected... tricky, eh.

  • "Here is a patch for IE 6.0, enjoy"
  • "Important microsoft update for Outlook"
  • "Microsoft XP patch. Install it now to protect yourself"
  • "Cool FREE screensaver"
  • "I send you this for your advice"
  • "Run attached file to see Britney Spears bare all!"
  • "A Nice game. It is my first game. Enjoy"
  • "Install this program to protect you from the Klez worm"
  • "Your computer is infected, run this program to remove the virus"
  • "You're a winner!"
  • "Here is a cool new screensaver"

As a general rule, you should avoid opening unsolicited email attachments whenever possible. 90-99% of the time, they are infected with a virus. Unsolicieted emails with attachements that end in the following file extensions should never be trusted. You should always scan them for viruses first.

File Extension Description File Extension Description
ADE Microsoft Access Project Extension MDB Microsoft Access Application
ADP Microsoft Access Project MDE Microsoft Access MDE Database
BAS Visual Basic® Class Module MSC Microsoft Common Console Document
BAT Batch File MSI Windows Installer Package
CHM Compiled HTML Help File MSP Windows Installer Patch
CMD Windows NT® Command Script MST Visual Test Source File
COM MS-DOS® Application PCD Photo CD Image
CPL Control Panel Extension PIF Shortcut to MS-DOS Program
CRT Security Certificate REG Registration Entries
EXE Application SCR Screen Saver
HLP Windows® Help File SCT Windows Script Component
HTA HTML Applications SHS Shell Scrap Object
INF Setup Information File URL Internet Shortcut (Uniform Resource Locator)
INS Internet Communication Settings VB VBScript File
ISP Internet Communication Settings VBE VBScript Encoded Script File
JS JScript® File VBS VBScript Script File
JSE JScript Encoded Script File WSC Windows Script Component
LNK Shortcut WSF Windows Script File
    WSH Windows Scripting Host Settings File

Microsoft never sends security updates via email. NEVER. So don't believe any emails claiming that they are a patch for any Microsoft products. Patches and updates for Microsoft products can ONLY be found on their website at this address...

A common trick to get you to open up an infected email is to have the sender be someone familiar to you. Don't open attachments even if it's from your mom. Chances are, your mom's computer was infected and the virus is now trying to use social engineering to spread to your machine.

Safe File Attachments

Image files cannot be infected so you can still send grandma pictures of the baby. It is generally safe to open an email attachment that end with .jpg .jpeg .png .gif .psd .tiff

Audio files that end in .mp3 or .wav can not be infected, however some .avi .mpg and .mpeg files can be infected.

You should still scan these files with your antivirus program. New viruses are discovered all the time.

Open Microsoft Word and Excel Documents with Caution

Many businesses need to e-mail Microsoft word documents and excel spreadsheets to their employees. Unfortunately, these files can become infected with devastating "macro viruses". If you absolutely HAVE to open one of these files you should first make sure that you have an antivirus program installed and operational on your computer. Then scan the document with your antivirus program before opening it.

You should always Microsoft Word and Excel documents for viruses even if they are from your boss or someone you believe to be trusted. Many new viruses can impersonate people so you never know who is really sending it. It could say it's from your boss, but it could really be coming from someone else.