Computer virus symptoms are a not cast in stone, but rather a moving target. Just like with the human viral conditions, they evolve through generations – which in computer technology terms may mean weeks or even days. Some symptoms may not necessarily mean an infection – for example, if you are sneezing, you do not necessarily have a flu, it may be just an allergy – which means different cause, and different treatment methods. Same with computers – if your system seems to be slower than usual, it may be a symptom of a virus, but it may also be a symptom of “program overload” – when you have too many programs running at once, and it crashes  your computer system’s performance.

There are literally dozens of different ways a computer can become infected with spyware, viruses, and other malware. Below is a list of the most common ways a computer can contract these infections listed in the order we believe are most commonly done.

Computer freezing:

Because viruses damage your hard drive, they can cause your computer to experience a catastrophic failure. If you're lucky enough that your computer still turns on after a crash, make sure to run antivirus software to determine whether a virus was the cause.

Slow Performance

This could be a symptom of many things, including infection by a virus. If it has been infected by a virus, worm or Trojan, among other things, which are running on the computer, they could be running tasks that consume a lot of resources, making the system run more slowly than usual.

Slow Startup

One of the most common computer virus symptoms is slow down. You can know that your computer has been affected by malware if your operating system, computer applications, and internet speed begin to slow down. If you note such a tendency and you’re not running heavy applications or programs, there may be cause for alarm.

System Crashing

If your programs or your system crash constantly or the infamous BSOD (Blue Screen of Death) appears regularly, it’s a clear warning that your system is not working properly and you should look into it. If your computer crashed, best course of action – Do Not Resuscitate and call your IT support company.

Missing files

It also may be due to virus infection. Many times when virus is infected in any computer, the files stored in hard drive start missing or deleted. So, if you find that any of your file is deleted or missing from your computer, it may be due to virus attack.