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What is a computer virus?

Here at NEWTON, we get a lot of questions on computer viruses, so we thought that we would provide a helpful guide that should help to answer all of your questions about them. Please see the questions below for what you are looking for. A special thanks to Mike Stewart for helping us answer these questions.

What are Computer Viruses?

Computer viruses are programs written by "mean" people. These virus programs are placed into a commonly used program so that program will run the attached virus program as it boots, therefore, it is said that the virus "infects" the executable file or program.

What Do Viruses Do?

Viruses have many purposes-some are designed to play annoying tricks, whereas others have destructive intent. Some viruses present themselves as jokes while performing secret destructive functions. There two major types of viruses are compiled viruses, which are executed by the operating system, and interpreted viruses, which are executed by an application.

How do Viruses Spread?

Viruses insert themselves into host programs and propagate when the infected program is executed, generally by user interaction (e.g., opening a file, running a program, clicking on a file attachment).

How do I prevent a virus?

  1. Load only software from original disks or CD's. Pirated or copied software is always a risk for a virus.
  2. Execute only programs of which you are familiar as to their origin. Programs sent by email should always be suspicious.
  3. Computer uploads and "system configuration" changes should always be performed by the person who is responsible for the computer.
  4. Password protection should be employed.
  5. Check all shareware and free programs downloaded from on-line services with a virus checking program.
  6. Purchase or download a anti-virus program that runs as you boot or work your computer. Up-date it frequently. There are free anti-virus programs availible.

What are Trojan Horse programs?

Named after the wooden horse from Greek mythology, Trojan horses are non-replicating programs that appear to be benign but actually have a hidden malicious purpose. Some Trojan horses are intended to replace existing files with malicious versions, whereas other Trojan horses add another application to a system without overwriting existing files. Trojan horses are often difficult to detect because they appear to be performing a useful function

What are Malware programs?

Malware is any "bad" software. It is a broad term for software (programs and scripts) that have malicious intent and is not specifically addressed in this pub. But Viruses, Trojans, and Key-loggers are just examples of Malware.

What are Phishing programs?

Phishing refers to use of deceptive computer-based means to trick individuals into disclosing sensitive personal information. To perform a phishing attack, an attacker creates a Web site or e-mail that looks as if it is from a well-known organization, such as an online business, credit card company, or financial institution. The fraudulent e-mails and Web sites are intended to deceive users into disclosing personal data, usually financial information. For example, phishers might seek usernames and passwords for online banking sites, as well as bank account numbers.

For more information, please check out the National Institute of Science and Technology which is the US government office in charge of this problem, at this URL:

The part about viruses is 5.1.1.

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