Common computer virus Symptoms

There are a lot of ways that a computer can start to act strangely for no good reason. These changes in behavior may be the result of a computer virus, but there are other possible explanations as well.

Computer too slow
The first thing to check if your computer is slow . A slowing in your computer can be the result of a number of circumstances — and a computer virus is definitely among them. The following list provides some considerations for making an educated guess as to why your computer is slowing down:

Have you made any changes to your computer lately? For instance, have you upgraded to Windows XP or Windows Vista ? These newer operating systems require a lot more memory than their predecessors.

Have you upgraded a program? Like Windows Vista and Windows XP, newer versions of many other programs like Microsoft Office and Microsoft Works require a lot more memory than earlier versions.

Have you  downloaded a lot of pictures or other information? Pictures and music take up space. If your hard drive is almost full, your computer will definitely run slower. If you’re sure you haven’t made any changes, then you may have a computer virus. You’ll have to check your computer’s behavior and run a number of simple tests before you can be sure.

Unexplained activity
Does your hard-drive or network-activity light flicker for no apparent reason? While there may be a legitimate reason for it, this could also be a sign that a computer virus or a hacker’s back-door program (a devious little program that allows secret access without your permission) is running on your computer. You might be broadcasting some of your computer resources to a hacker and be largely unaware of it. Here are some examples of what could be going on if a hacker has gotten control of your computer:

The hacker could be using your computer to send thousands, even millions, of those annoying spam messages to people all over the Internet.
The hacker could be using your computer to launch attacks on corporate computing networks.
The hacker could be using your computer to scan other networks, hunting for vulnerable ports (communication channels for particular computer processes) that can mean more potential-victim computers.
The hacker may have installed spyware that reports back to the bad guys without the your knowledge. One example is a key logger — a small program that records every key press and mouse movement in an attempt to learn your bank-account numbers, credit-card numbers, and other sensitive information that you probably don’t want strangers to know about. 

Crashes or hangs
Does your computer crash often? Does it just stop responding? Do you often get the Blue Screen? Again, there are many possible explanations. Crashing, hanging, and blue screens may be computer virus-induced, but they’re probably not. These maladies are more likely the result of new software, new drivers, or even a hardware component that’s beginning to fail. Check out those possibilities first.

Will not boot
Boot used to be a noun — the leather thing you put on your foot to protect it from rough terrain. These days boot is a verb just as often; it’s the process that your computer performs to start itself when you turn it on or press Ctrl+Alt+Del. Just because your computer won’t boot, it doesn’t necessarily mean that your computer has a computer virus. Maybe yes, maybe no. There are several other likely explanations — for example, a corrupted master boot record  or damage to an important file that your computer uses to start up. If either of these was the case, you’d probably have to rebuild your computer’s operating system and file system from scratch.

 

Strange computer behavior
Computers sometimes behave inscrutably, but their behavior should be predictable. Same deal for computer computer virus — which means they can’t completely conceal their activities. You can look for the devil in the details. Perhaps the signs are obvious (the colors go all weird, the computer puts words on-screen by itself, or it makes strange noises) or relatively subtle (your screen borders pinch inward for an instant just before you send e-mail). Time to observe closely and take notes. For openers, consider some “obvious” symptoms:
Files are not where you left them, and can’t be found on your computer- you might have a computer virus.
You can find the file, but its size or date stamp is suspiciously different. computer viruses that infect program files may make the files bigger or smaller than they should be, or change their date stamps. Date stamps don’t ordinarily change on program files — ever — unless an official software patch changes them.
On-screen text starts to change by itself. In the old days of the DOS command prompt, one computer virus made the letters in on-screen text seem to move around. Sometimes they changed colors, or started consuming each other like Pac-Man. Bad sign.
An out-of-context message appears on-screen. Some computer viruses announce their presence by taunting the user. If you are greeted with a message such as Your computer is now Stoned!, you probably have a computer virus.