What are the symptoms of an infected computer?

It’s not always easy to tell if your computer has been compromised. More than ever before, the authors of viruses, worms, Trojans and spyware are going to great lengths to hide their code and conceal what their programs are doing on an infected computer.

 It’s very difficult to provide a list of characteristic symptoms of a compromised computer because the same symptoms can also be caused by hardware and/or software problems. Here are just a few examples:

• Your computer behaves strangely, i.e. in a way that you haven’t seen before.
• You see unexpected messages or images.
• You hear unexpected sounds, played at random.
• Programs start unexpectedly.
• Your personal firewall tells you that an application has tried to connect to the Internet (and it’s not a program that you ran).

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Threat Types

Threats to your computer system, data, and identity come in many different forms, a few of the most common are listed as follows:

Viruses:

A virus is a self-replicating program that is designed to damage or degrade the performance of a computer. A virus is replicated by being copied or by initiating its copying to another program, computer boot sector or document. Viruses can be classified into four different categories as follows:

File Infector

A File infector virus when executed on a system will seek out other files and insert its code into them. The programs with .EXE and .COM extensions are the most commonly targeted, but a file infector virus can target any executable file.

This infection is most commonly distributed via compromised networks, over the web via drive-by, or from a corrupted media (CDRW, flash media).

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