Examples of Threats:
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Modify, corrupt, or destroy files on your computer
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Corrupt the computer operating system causing unpredictable behavior, poor performance, or security holes
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Unauthorized e-mailing of files or the virus itself to people on your contact list
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Allow a hacker to gain control of your computer through a back door
Our Tips:
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Enable antivirus protection at your Internet service provider (ISP) and/or e-mail provider if it is available.
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Install antivirus software on each computer in your home network.
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Set up antivirus software to automatically perform periodic virus scans.
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Make sure any antivirus software automatically retrieves signature updates.
What Are Computer Viruses?
The term computer virus tends to get used for any malicious code created with the intention of harming a computer or slowing network traffic, but a virus is actually a specific type of program. The next few sections give a brief overview of the different kinds of malicious software often lumped into the term virus, including a real-world example of each.
Very Important
You might notice that throughout this book (or any of our books) that we do not name specific viruses, worms, Trojan horses, adware, spyware, and so on. The reason is that one motivation for people who create such programs is the notoriety and publicity that they can create. So, we just choose not to add fuel to that fire.
Viruses
The definition of a computer virus is a program that attaches itself to (or really within) another program (the host) so that it can replicate itself when the host program is run or executed. That's it. You might be surprised that this definition says nothing about removing data, crashing a computer, or any other nasty effects. This is because a virus is defined by its replication behavior, not its effect on the host computer. That said, many viruses do harm data and computers (either intentionally or unintentionally), and any program activity that occurs on your computer or network without your knowledge or consent is a hostile attack against you and your property.
You might think it is okay because it is from a friend or seems harmless because you did share pictures recently, so you double-click the attachment, installing a virus on your computer. The virus then searches through your Microsoft Outlook Express address book and e-mails a copy of itself to all your friends and family.
Some viruses are designed to remove or replace data or corrupt computer systems. These types of viruses tend to be an exception, because they are extremely difficult to create. Just as worrisome are the viruses created by people who are not skilled programmers, because their programs tend to be unpredictable. In the off chance that a virus created by an unskilled programmer does replicate in the "wild" (on the Internet), there is really no telling what the program will do.