Networking All-in-One For Dummies
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Viruses are one of the most misunderstood computer phenomena around these days. What is a virus? How does it work? How does it spread from computer to computer?

What is a virus?

Make no mistake — viruses are real. Now that most people are connected to the Internet, viruses have really taken off. Every computer user is susceptible to attacks by computer viruses, and using a network increases your vulnerability because it exposes all network users to the risk of being infected by a virus that lands on any one network user’s computer.

Viruses don’t just spontaneously appear out of nowhere. Viruses are computer programs that are created by malicious programmers who’ve lost a few screws and should be locked up.

What makes a virus a virus is its capability to make copies of itself that can be spread to other computers. These copies, in turn, make still more copies that spread to still more computers, and so on, ad nauseam.

Then, the virus patiently waits until something triggers it — perhaps when you type a particular command or press a certain key, when a certain date arrives, or when the virus creator sends the virus a message. What the virus does when it strikes also depends on what the virus creator wants the virus to do. Some viruses harmlessly display a “gotcha” message. Some send an email to everyone it finds in your address book. Some wipe out all the data on your hard drive. Ouch.

Many years ago, in the prehistoric days of computers, viruses were passed from one computer to another by latching themselves onto floppy disks. Whenever you borrowed a floppy disk from a buddy, you ran the risk of infecting your own computer with a virus that may have stowed away on the disk.

Virus programmers have discovered that email is a very efficient method to spread their viruses. Typically, a virus masquerades as a useful or interesting email attachment, such as instructions on how to make $1,000,000 in your spare time, pictures of naked celebrities, or a Valentine’s Day greeting from your long-lost sweetheart. When a curious but unsuspecting user opens the attachment, the virus springs to life, copying itself onto the user’s computer — sometimes sending copies of itself to all the names in the user’s address book.

After the virus works its way onto a networked computer, the virus can then figure out how to spread itself to other computers on the network. It can also spread itself by burrowing into a flash drive so that when the flash drive is inserted into another computer, that computer may become infected as well.

Here are some more tidbits about protecting your network from virus attacks:

  • The term virus is often used to refer not only to true virus programs (which are able to replicate themselves) but also to any other type of program that’s designed to harm your computer. These programs include so-called Trojan horse programs that usually look like games but are, in reality, ransomware.
  • A worm is similar to a virus, but it doesn’t actually infect other files. Instead, it just copies itself onto other computers on a network. After a worm has copied itself onto your computer, there’s no telling what it may do there. For example, a worm may scan your hard drive for interesting information, such as passwords or credit card numbers, and then email them to the worm’s author.
  • Computer virus experts have identified several thousand “strains” of viruses. Many of them have colorful names, such as the I Love You virus, the Stoned virus, and the Michelangelo virus.
  • Antivirus programs can recognize known viruses and remove them from your system, and they can spot the telltale signs of unknown viruses. Unfortunately, the idiots who write viruses aren’t idiots (in the intellectual sense), so they’re constantly developing new techniques to evade detection by antivirus programs. New viruses are frequently discovered, and antivirus programs are periodically updated to detect and remove them.

Antivirus programs

The best way to protect your network from virus infection is to use an antivirus program. These programs have a catalog of several thousand known viruses that they can detect and remove. In addition, they can spot the types of changes that viruses typically make to your computer’s files, thus decreasing the likelihood that some previously unknown virus will go undetected.

Windows comes with a built-in antivirus program called Windows Defender. Although it is serviceable, better alternatives are available. Popular options include Avast, which is free and provides significantly better protection than Windows, Symantec Security by Symantec, and VirusScan Enterprise by McAfee.

The people who make antivirus programs have their fingers on the pulse of the virus world and frequently release updates to their software to combat the latest viruses. Because virus writers are constantly developing new viruses, your antivirus software is next to worthless unless you keep it up to date by downloading the latest updates.

Here are several approaches to deploying antivirus protection on your network:
  • Install antivirus software on each network user’s computer. This technique would be the most effective if you could count on all your users to keep their antivirus software up to date. Because that’s an unlikely proposition, you may want to adopt a more reliable approach to virus protection.
  • Managed antivirus services place antivirus client software on each client computer in your network. Then, an antivirus server automatically updates the clients on a regular basis to make sure that they’re kept up to date.
  • Server-based antivirus software protects your network servers from viruses. For example, you can install antivirus software on your mail server to scan all incoming mail for viruses and remove them before your network users ever see them.
  • Some firewall appliances include antivirus enforcement checks that don’t allow your users to access the Internet unless their antivirus software is up to date. This type of firewall provides the best antivirus protection available.

Safe computing

Besides using an antivirus program, you can take a few additional precautions to ensure virus-free computing. If you haven’t talked to your kids about these safe-computing practices, you had better do so soon.
  • Regularly back up your data. If a virus hits you, and your antivirus software can’t repair the damage, you may need the backup to recover your data. Make sure that you restore from a backup that was created before you were infected by the virus!
  • If you buy software from a store and discover that the seal has been broken on the disc package, take the software back. Don’t try to install it on your computer. You don’t hear about tainted software as often as you hear about tainted beef, but if you buy software that’s been opened, it may well be laced with a virus infection.
  • Use your antivirus software to scan your disk for virus infection after your computer has been to a repair shop or worked on by a consultant. These guys don’t intend harm, but they occasionally spread viruses accidentally, simply because they work on so many strange computers.
  • Don’t open email attachments from people you don’t know or attachments you weren’t expecting.
  • Use your antivirus software to scan any floppy disk or CD that doesn’t belong to you before you access any of its files.

About This Article

This article is from the book:

About the book author:

Doug Lowe is the bestselling author of more than 40 For Dummies books. He's covered everything from Microsoft Office to creating web pages to technologies such as Java and ASP.NET, and has written several editions of both PowerPoint For Dummies and Networking For Dummies.

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