If your computer is running slower than usual, doesn’t boot up, or has other such problems, your computer is likely to be affected by a virus. What exactly is a virus, and how can it affect you? Read on to learn more.

What is a virus?

A virus, or worm, is a computer program that can spread across computers and networks by making copies of itself, usually without the user’s knowledge.

The term “virus” is a widely used term that actually applies to three different kinds of malicious programs viruses, worms, and Trojan horses.

Viruses can have harmful effects, including displaying irritating messages and disrupting your productivity, to stealing data or giving other cybercriminals control over your computer. They can even enable them to format or modifying data on your hard drive.

According to the Tech Encyclopedia, a computer virus “may be a simple prank that pops up a message on screen out of the blue, or it may destroy programs and data right away or on a certain date. It can lie dormant and do its damage once a year. For example, the Michelangelo virus contaminates the machine on Michelangelo’s birthday.”

Why are they called viruses?

Computer viruses are called viruses because they share some of the traits of biological viruses. For example, a computer virus passes from computer to computer just like a biological virus passes from person to person.

A biological virus remains inactive until it enters the host cell. Once it has entered it uses the host cell’s normal mechanisms to reproduce itself. Similarly, a computer virus piggybacks on top of a program or document, replicates itself and harms the resources.

How Can Your Computer Catch a Virus?

There are two ways for your computer to get a virus:

  1. You load the virus onto your computer through an infected floppy, USB flash drives, CD-ROM, or other storage mediums.
  2. The virus arrives on your computer through a downloaded file, email attachment, or other another source on the Internet or a network. The large majority of such malicious programs are spread through the Internet.

How do they spread?

Many viruses are hidden in the code of legitimate software programs. These viruses are called file infector viruses, and when the program is launched, the code for the virus is also run, and in this way, the virus loads itself into your computer’s memory. From there, the virus searches for other programs on your system that it can infect – if it can find one, it adds its code to the new program, which is now infected as well and can be used to infect other computers.

Viruses wouldn’t be so destructive if all they did was replicate themselves. Unfortunately, most viruses have some sort of destructive attack phase where they do damage. Some sort of trigger (such a specific date, number of times the infected file should to be executed, or even an online hacker in control of the virus) activates the attack phase of virus which starts damaging the system.

What kinds of viruses are there?

All computer viruses do not behave, replicate, or infect the same way. Below are some of the most common types of malicious programs (commonly called viruses).

Trojan horse: ATrojan horse is simply a computer program. The program claims to do something useful (it may claim to be a game), but instead damages your PC when you run it (it may erase your hard disk). Trojan horses do not replicate themselves.

Worms: A program that replicates itself over a computer network and usually performs malicious actions, such as using up the computer’s resources and possibly shutting the system down.

A worm has the capability of reproducing greatly and travel across networks, allowing the worm to consume high levels system memory (or network bandwidth), causing Web servers, network servers and individual computers to stop responding.   For example, the Blaster worm in 2003 exploited vulnerabilities in Windows OS and let users know of its presence with a system shutdown warning.

Macro Virus: A macro virus is a virus that is written in a macro language (a language built into a software application such as a word processor). Macros are used to automated actions in such programs. These viruses affect the applications which support macro languages like Microsoft Word and Excel.

Uninfected documents can contain normal macros. A macro virus infects a computer by replacing these normal macros with the malicious code. The macro virus replaces the regular commands with the same name and runs when the command is selected. Most malicious macros run automatically when a document is opened or closed. According to some estimates, 75% of all viruses today are macro viruses. Once a macro virus gets onto your machine, it can embed itself in all future documents you create with the application.

Email Viruses: An e-mail virus is computer code sent to you as anattachment which, if activated, can cause unexpected and usually harmful effects, such as destroying certain files on your hard drive and causing the attachment to be emailed out to everyone in your address book. The Melissa virus and the ILOVEYOU virus are most famous e-mail viruses.

How can you protect your computer?

  • Use a safer operating system, such as one based on UNIX. Examples include Mac OS X and Linux distributions.
  • Install well-known and reputable antivirus software. SecurAid recommends free software such as Avast and AVG. The best paid antivirus on the market currently is Norton.
  • Scan your hard drive for viruses periodically. It is usually possible to set up scheduled scans in your antivirus or malware scanner, such as Malwarebytes Anti-Malware.
  • Update the antivirus software at least once a week. A good antivirus program will automatically update itself everyday if connected to the internet.
  • Turn off auto run on USB drives (i.e. turn off the automatic pop-up window when a USB is inserted).
  • Never run an e-mail attachment with executable program. A file with extension such as .exe, .com or .vbs is executable. If you run a malicious program, you have given it permission to do anything on your machine. Running an antivirus can help prevent this, as they automatically scan downloaded files for malicious software.
  • Keep backups of your data, especially important documents and other personal information.
  • Before you load a file or install software onto your computer from an outside source, such as USB drives or CD’s, use your antivirus program to scan the source.
  • If you receive an email attachment from an unfamiliar email address, or an attachment you were not expecting, either scan it or delete it (the latter preferred).

Virus Hoaxes

Sometimes you’ll get an e-mail from a friend warning you about the “latest virus” that you should be aware of and panic over. Many times, these viruses aren’t real. Even if someone who’s into computers warns you about a virus, don’t necessarily take it as a definite truth. Most major security software vendors maintain a list of virus hoaxes. You can check with these Web sites to see if a virus is legitimate or a hoax. Such a site would be http://securityresponse.symantec.com/avcenter/hoax.html.

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