...information from Internet ScamBusters
Note: This information isn't meant to scare you. It's meant to educate you, so that you can defend yourself properly.
What Is a Computer Virus?
Like viruses that infect living beings, computer viruses infect your computer. They are software, and are often attached to other software or documents you might receive. When you run the virus's software or the file the virus has infected, the virus can infect your computer's software.
There are many types of viruses and terms for them, but we'll use the general term 'virus' to make things easy.
Like the flu virus, a computer virus must spread from host to host to survive. When we get the flu, we cough and sneeze, and tiny particles carrying the virus spread the flu to other people.
With computer viruses, the virus is designed to spread from your computer to other computers. Here are some of the most common ways they spread:
1. Once the virus has infected your system, it may automatically send out emails containing more copies of the virus using the address book in your email program. This type of virus is called an Internet "Worm," because it is a self-propagating virus. For example, an Internet worm crippled tens of thousands of computers and slowed down parts of the Internet on the weekend of January 29, 2003.
2. If the virus is a macro virus (attached to a Microsoft Word document, for example), it may attach itself to any document you create or modify. If you send another document to someone by email, the virus goes along with it.
3. Sometimes viruses masquerade as a fun program (like an electronic greeting card) that secretly infects your system. If you pass the program along, not realizing that it contains a virus, you will be transmitting the virus manually to your friends, family, or colleagues.
Trojan Horses are closely related to computer viruses, but they differ in that they do not attempt to replicate themselves. More specifically, a Trojan Horse performs some undesired -- yet intended -- action while, or in addition to, pretending to do something else. A common example is a fake login program, which collects account information and passwords by asking for this info just like a normal login program does.
Many computer viruses are malicious -- in other words, they can erase your files or lock up whole computer systems. Other computer viruses are more benign -- they don't do any direct damage other than by spreading themselves locally or throughout the Internet.
Regardless, computer viruses should always be treated.
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