geeklog- ultimate geek knowledge: Signs of Infection : How to know what are the signs of Virus Infection? : Concerning Viruses II

There are a number of signs which show that a computer is infected. If you notice that your computer is doing strange things, specifically:

Unexpected messages or images appear on your screen or you hear unusual sounds;

The CD/DVD-ROM tray opens and closes unexpectedly;

The computer arbitrarily opens a program without your assistance;

Warnings pop up on the screen about a program on your computer attempting to access the Internet, even though you initiated no such action, then, it is highly probable that your computer has become infected with a virus.

There are also several typical traits of a virus infection through e-mail:

Friends or acquaintances tell you about messages from you that you never sent;

Your inbox houses a large number of messages without return addresses or headers.

It must be noted that these signs can results from problems other than viruses. They can sometimes arise from different causes. For example, in the case of the e-mail, infected messages can be sent with your return address but not from your computer. There are also indirect indications that your computer is infected:

Your computer freezes or crashes frequently;

Your computer loads programs slowly;

You cannot boot up the operating system;

Files and folders disappear or their contents are distorted;

The hard drive is frequently accessed (the light blinks);

The web browser (for example, Microsoft Internet Explorer) freezes up or behaves unexpectedly (for example, you cannot close the program window).

In 90% of cases, these indirect systems are caused by malfunctions in hardware or software. Despite the low likelihood that these symptoms are indicative of infection, a full scan of your computer is recommended.

What to do if you show signs of infection...?

If you notice that your computer is behaving suspiciously...

Don't panic! Do not give in to panic. This is the golden rule, and it could save you from losing important data and from a lot of fretting.
Disconnect your computer from the Internet or local network, if it is on one.
If the infection symptom is that you cannot boot from the computer's hard drive (the computer displays an error message when you turn it on), try booting in safe mode or with the emergency Microsoft Windows boot disk that you created when you installed the operating system on the computer.
Before doing anything else, back up your work on removable storage media (floppy, CD/DVD, flash drive, etc.).
Install a good antivirus software, if you have not done so already.
Update databases and program modules. If possible, get the updates off the Internet from an uninfected computer at a friend's, an Internet café, or work. It is better to use a different computer, since when you connect to the Internet with an infected computer, there is a chance that the virus will send important information to hackers or spread the virus to the addresses in your address book. That is why if you suspect that you have a virus, the best thing to do is to immediately disconnect from the Internet.
Select the security level recommended by the experts of the Antivirus program you used or installed.
Start a full computer scan.

Related Links:

The information presented herein is adapted from Help and Support Section of the Kaspersky Anti-Virus 7.0, details of the notes can be pertained from related links as following: