A computer virus is a program that can copy itself and spread across one or more computers when they are connected to a network without the knowledge of the user. Viruses can be particularly tricky to remove from your computer because they can self-modify or change over time as they copy themselves.
Fortunately, viruses can only spread across multiple computers if an uninfected computer is connected to a network, or if the computer gets connected to infected media such as a USB drive or a CD.
Do you suspect your computer might be infected with a virus?
Look for these tell-tale signs:
Computer is running more slowly than usual
If your computer runs slowly upon start-up, you may have a virus. Common signs are having to wait a long time to perform simple tasks such as checking e-mail or opening files. In really serious cases, your mouse pointer may even lag as it moves across the screen.
Locks up or crashes frequently
Does your computer frequently just stop working or otherwise lock up, causing you to have to restart your computer? This phenomenon is also called freezing or freezing up. If your computer locks up often and/or suddenly, a virus could be the culprit.
You cannot access your disks
If you are having trouble accessing your internal hard drives or external disk drives, your computer may have a virus. For example, if you click on your directory and cannot gain access to your disks, this is a tell-tale sign you may have a virus.
You cannot print items correctly
Printer performance an also be affected by the presence of a virus. For example, if your printers are not accessible or if the printing results are not satisfactory, this could be a sign of a virus at work.
Your anti-virus software is disabled for no apparent reason
Most computers ship with anti-virus software pre-installed. The best anti-virus products should be more than sufficient in keeping your computer protected. However, you know you have a serious problem if your anti-virus software itself seems to be repeatedly disabled upon start-up or when you try to run a virus scan. The most dangerous viruses can actually try to block your anti-virus software from working properly (for obvious reasons), which effectively renders your computer open to all potential invaders.
Viruses are not the only things that can cause performance problems for your computer. Other common causes are malware, adware, spyware, and registry problems. If your computer is not performing properly, you should explore all possibilities, including these other common causes of degraded performance.
Types Of Threats
Virus : Malicious software that attaches itself to an existing program. Upon execution of the existing program, the virus code activates and begins attaching copies of itself to other programs in the system. Infected programs may then copy the virus to further programs.
E-Mail Virus : A virus that travels in e-mail attachments. Upon opening an infected attachment, this type of virus commonly replicates by automatically mailing itself to contacts in the victim’s e-mail address book.
Worm : Software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. When it finds the desired security hole, the worm copies itself to the new machine and begins replicating from there as well. For users that are not on a network, a worm can still travel via your Internet connection; and in some cases open a “backdoor” that allows hackers to take over your computer or collect personal information for distribution to others.
Trojan horse : A program that claims to be one thing (such as a game), but instead causes damage when it’s run. For example, a Trojan horse may erase all data on your hard disk drive. Unlike e-mail viruses and worms, Trojan horses have no way to replicate automatically.