How To Recognize If Your Computer Has A Virus Or Trojan On It

    June 22, 2005

It isn’t always easy to tell if your computer has become infected with a virus or similar anti-social piece of software.

Normally, your antivirus software will locate and identify any malicious programs that find their way onto your computer. However, in the event that you haven’t yet installed the antivirus software, or have let it get out of date (shame on you), here are a few things to look for as clues that you have an infection of some sort on your machine.

Disk Space Reduction

The disk space reduces suddenly without any cause – this is because many viruses create multiple copies of themselves every time the disk is accessed. These copies are normally made by attaching the virus code to already existing programs on your system. This increases the file size of the newly infected file and reduces the amount of space on your drive even though you did nothing.

Directory Structure Damage

Some viruses destroy directory structure to achieve replication. When this happens, when you try to view the contents of that folder, you may see garbage and/or incorrect files displayed on the screen.

File Allocation Tables (FAT) Damage

File allocation tables are used by Microsoft T operating systems to manage all data on computer disks. They are basically a complex record of what and where all data is located on your computer’s disks. By destroying FAT, considerable data loss can happen very easily. This type of damage is not limited to MicrosoftT operating systems. All computer systems have some sort of disk data management system, and viruses are designed to attack any of them.

Improper Disk Function

Some viruses, when in memory, watch all disk activity and divert the system to access the disk in an improper, unwanted and damaging manner. This can often be noticed by increased disk activity (for instance your disk is always active), slower open and save times, and generally slow disk performance.

Hard drive noise

Some viruses watch all disk activity and when the conditions for infection are matched the virus will check for targets on the disk and infect/destroy them if found. This search, infection, destruction requires some extra time and more disk rotations, which is often indicated by more hard drive noise, the hard drive never stopping, or simply taking longer than normal to access your files. Unfortunately, these symptoms also develop when you need to defragment your disks. A good commercial virus checker will let you which is the case.

Drive light glows without any reason.

When some viruses take control they search for their target on all drives they can possibly access. As a result drive lights may glow (turn on) without you actually doing anything that accesses the disk (saving a file, loading a file).

If you find that your computer is accessing the hard drive more and more frequently while you are doing nothing that access the hard drive (like reading an email for example), you may want to perform a complete system scan with your antivirus software to rule out a possible virus or spyware infection.

Increased Number or size of Files.

Viruses often create new files to store their own code in separate files. Generally such newly created files are hidden. However if you suddenly start to lose disk space, it can often be a sign of a virus creating hidden files on your hard drives. Some viruses increase size of the executable files, while infecting them, as they attach their own code to them.

Change in Date/Time Stamp of the File.

Some viruses do not restore the old date/time stamp of a file after infecting it, hence date/time stamp of the file is the date/time stamp of the virus infection. Look out for other odd things like when the ‘seconds’ entry of a time-stamp shows more than 60 seconds.

Funny things happening with your screen

Viruses can use the screen for other activities than just for displaying the message. Some viruses are specially designed to play with the screen such as they can highlight some pixel character or can increase intensity of some pixel or display bouncing balls on screen etc. Some viruses show effective animated pictures e.g. a dancing girl on your screen while in background the virus is busily formatting your hard disk.

These few things represent clues to an infection – you could say they are all when your PC starts doing odd things. Relying on figuring out you’re infected isn’t really a very smart solution, since any damage could well be done before you notice. What you need to do is to take decent precautions to prevent the infection in the first place. Step one is almost undoubtedly buying and running antivirus software from one of the major suppliers.

To learn more about effective, easy to afford and use PC protection tools, visit

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