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:
- 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.
- 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.
- 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.
What Kind of Damage Can Computer Viruses Do?
The damage a computer virus can inflict on your system depends on many things, including how sophisticated the virus is. Here is a short listing of the types of damage viruses can do to your computer — they can really hit you where it hurts:
– Some viruses can delete or change files. Some viruses will delete all of your documents, or even reformat your hard drive, making your computer unusable.
– Some viruses can release confidential information like credit card information, account numbers, and passwords by emailing it to random email addresses or the address of the virus writer.
– Some viruses can slow down your system dramatically.
– Some viruses plant monitoring software or change security settings that allow hackers to enter your computer without you knowing about it and steal information or control it.
Other viruses, like the Internet worm that hit recently, also can have widespread effects on computer networks and the Internet.
Your Computer May Have a Computer Virus If…
How do you know if you have a computer virus? If you’re not running an anti-virus program (see the next section), you may not know at all since many viruses are benign.
Some symptoms of a virus infection are:
– Your computer displays strange messages, plays music, or shows odd graphic displays.
– Your computer takes longer to boot up, operates more slowly than usual, and takes longer to start programs.
– Your computer has much less memory or hard drive space available.
Some legitimate software can cause these symptoms, so the only way you can be sure your computer is virus-free is to regularly scan it for viruses using anti-virus software.
How Can Your Computer Catch a Virus?
There are only two ways for your computer to get a virus:
- You load the virus onto your computer through an infected floppy, CD-ROM, or other storage medium.
- The virus arrives by a downloaded file, email attachment, or other method from the Internet or a network.
At this point, an infected file is on your computer’s hard drive. But remember, your computer will only become infected if you launch or view the file, or run the infected program.
So an important tip is to always scan new files for viruses before you use them.
Take these precautions when working with files and the Internet:
– Before you load a file or install software onto your computer from a floppy disk or CD-ROM, use your anti-virus program to scan the floppy or CD.
– If you receive an email attachment from an unfamiliar email address, or an attachment you were not expecting, either scan it or delete it (preferred).
– If you receive an email attachment from someone you know, and your anti-virus program does not automatically scan incoming emails, save the attachment to your hard drive and scan it with the anti-virus program. Your friend or colleague’s computer may be infected with a virus.
– When you download software from the Internet, be sure to download it from the software company’s site or a recognized download site. Download the file to your hard drive and scan it using your anti-virus program before you run or decompress it.
– If someone sends you a ‘joke’ file or electronic greeting card that you must launch to view, be very wary.
– Don’t use Outlook or Outlook Express as your email program. More viruses are spread from the security holes in Outlook than any other email program.
Many experts now feel that the dangers of being infected by a virus are so great that it just isn’t worth receiving email attachments. You can set your email program to stop accepting them.