Computer Virus Symptoms
Keep an Eye on These Virus Symptoms

Paying attention to Computer virus symptoms can prevent major damages to your computer. This page will explain all symptoms of Computer viruses that you must be aware of.

It isn’t always easy to tell if your computer has become infected with a virus or similar anti-social piece of software. Most normally, your antivirus software (if you have one) 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 However, in the event that you haven’t yet installed the antivirus software, or have let it get out of date (shame…), here are a few things to look for as clues that you have an infection of some sort on your machine.

Disk Based Computer Virus Symptoms

Disk Space Reduction

The disk space reduces suddenly without any cause or reduction in disk space continues when the disk is being accessed (disk Input/Output operation). 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 intentionally to achieve replication, and some do it unintentionally. For example, some boot sector viruses store data in the root directory of your computer (C:\\\\\\\\ ) and cause loss of directory information. 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 ™ 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.

Some viruses whose only aim is destruction, prefer to destroy FAT or other directory data. If FAT is corrupted, repair utilities (like Norton Utilities) will show incorrect data linking patterns for the files on your machine. This type of damage is not limited to Microsoft™ 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

This is one of the common computer virus symptoms. Some viruses, when in memory, watch all disk activity and divert the system to access the disk in an improper/unwanted/damaging manner. This type of viruses can often be noticed by increased disk activity (it is always active),slower open and save times, and generally slow disk performance.

The above disk based computer virus symptoms are a clear indication of an infected Computer.

Hardware Based Symptoms

More Rotations of the Disk

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. This 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 (Norton, McAfee, Pc-Cillin) will let you which is the case. Having said that, it is also a good idea to make use of a good, automatic disk defragmenting tool like the one in Norton Utilities. It is automatic, and can be easily set to manage all your hard drives on a regular schedule (at night for example when you don’t use your machine).

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 (typing an email for example), you may want to perform a complete system scan with your antivirus software.

If you have configured your virus scanner for auto background scanning or scheduled scanning then it may access the hard drive without you doing anything. You may misunderstand this as one of the hardware based computer virus symptoms.

File Based Symptoms of Computer Viruses

Increased Number 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.

Increased Size of the Executable Files

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.

Invalid Date/Time Stamp of the File

Some viruses use this section (from directory structure) of the files to store their infection marker, which makes it invalid. E.g. The 'seconds' entry of a time-stamp shows more than 60 seconds.

Screen Based Computer Virus Symptoms

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. Dancing girl while in background they do something nasty like format your hard disk.

Even though the above are the most common Computer virus symptoms it does not mean that there are no other symptoms. The rule of thumb is if you notice a strange behaviour in your computer then this may be a symptom of a virus.

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