Computer Viruses: How do they work?

I first heard of this term called Computer Virus when i was 10 years old and that was 15 yrs back. Since then, Computer Viruses have matured both in the way they attack and the coding that goes behind them.

A computer virus is nothing but a small software which piggybacks itself onto some other program. An example to illustrate this definition can be a virus which gets attached to Microsoft Word. Each time Word runs, the virus attached also gets executed.

 Computer Virus

[Image Source: http://blog.fotogenia.info]

The lifecycle of a computer virus goes through these phases:

  1. Coding/Visualizing the virus: In this phase, the developer of the virus, codes and develops the virus by visualizing the intent of the virus.
  2. Releasing the virus: The virus once ready, is released to the outer world.
  3. Spreading the infection: In order for the virus to be able to make an impact, it needs to be spread, this is often done using techniques like autoforwarding a simple email to all the contacts in your address book. ( there are though many other popular techniques)
  4. Quarantining the virus: In this phase, the virus gets Quarantined. The Quaranting process actually takes sometime. This happens only after the antivirus firms validate the signature of the virus and develop an antivirus update. The virus is then Quarantined.

Also read: How does Email Scanning Work?

More to read: Top 3 FREE Antivirus Applications

In order to prevent the spreading of application using the method mentioned above, Microsoft Applications come built in with a technique called Macro Virus Protection. Macro Virus Protection by default is turned ON. With this feature turned ON, the auto-execute feature is disabled. This ensures that when a viral code is trying to execute itself, a  dialog pops up warning the user.

Macro Virus Protection in Microsoft Word 2000, 2002, and 2003

Macro Virus Protection

Macro Virus Protection in Word 2000, 2002 and 2003 can be configured by going through the steps mentioned below

Open Word  from the Tools menu, select Macro and then click on Security

  1. In the resulting window, click on the tab mentioned as Security Level.
  2. You will then have the option to choose one of the security levels.
  3. Select Very High to allow only macros installed in trusted locations to run. Any other macros, signed or unsigned, are disabled. (This setting is available only in Word 2003.)
    Select High to allow only signed macros to run.
    Select Medium to be prompted to run macros.
    Select Low to run all macros.

Now, with the tool activated, if you load a suspect file, Word will warn you that the document contains macros and will ask you what to do about them. You can select Disable Macros to avoid infection from a file containing a macro virus.

Note: If you close the file and reopen it, or if you open an additional file with macros, you will get the same warning, and you must select Disable Macros again.

Tips on Protecting yourself from Computer Viruses:

  • Get a good Antivirus Software.
  • Keep the Antivirus Software updated with latest Virus signatures.
  • Use an Internet Firewall.
  • If you use Microsoft Windows, Visit Microsoft Update and turn on automatic updating.
  • Never open an e-mail attachment from someone you don’t know.
  • Avoid opening an e-mail attachment from someone you know, unless you know exactly what the attachment is. The sender may be unaware that it contains a virus.

Also read: How does Email Scanning Work?

More to read: Top 3 FREE Antivirus Applications

Do comment if you find this useful.

Cheers,
Vaibhav

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5 Responses

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