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50,000 computer viruses created with approximately 500 always active.

Some Viruses can Crash your PC.

People have a very general view that there are many types of computer viruses and are those programs that cause damage or make the system crash.

Malicious code is the general word used and virus is one type of malicious code. Worms and Trojans are different from computer virus and destructive types of worms are sometimes termed as internet types of virus. Computer viruses have made their mark on the PC's since the 90's with different types of viruses causing damage to computers.

The earliest viruses made the most impact as no anti-virus programs were available. The advent of anti-virus programs spelled a death blow to many common types of computer viruses that were written by the various tools to generate types of computer virus. Those who were inept at programming used these various tool to generate the virus. Devious mind always find new ways when they found that the anti-virus software's were able to disinfect and remove the different types of computer viruses they went on to new methods and that is how Trojans and worms came up.

There are a few main types of computer viruses and these computer virus types are classified below depending upon the infection methods:

Boot sector/Master Boot Record Computer Virus

Means of Infection

Boot sector is that area of the computer that is accessed when the computer is turned on. A boot sector virus infects this portion. Once the boot sector is infected the virus is loaded into memory when the computer is turned on. This virus then infects boot sectors on floppies or other removable media Master Boot record virus only infects the Master boot record and not the boot sector

Damage Caused

Boot sector viruses gain complete control of the master boot record or the DOS boot sector by replacing the operating system contents with that of its own. This allows the virus to spread fast and cause damage:

  • By gaining control of the master boot record and the DOS boot sector the boot sector viruses can sometimes hide the resources that the computer has( the floppy drive even though attached may not be present)
  • Some boot sector viruses contain instructions to redirect disk reads.
  • Some boot sector viruses move the master boot record to another location causing the system to crash when it boots up. Other boot sector viruses cause damage to the master boot record
  • Some boot sector viruses damage the File Allocation Table (FAT) which is the index of all the files on the drive. This causes loss of data

Other Types of Viruses

A type of computer virus that normally shares a few characteristics of worms or Trojans or other methods used by the main types of computer viruses is differently classified. The nomenclature used is different. We detail some of those below.

Multi-Partite Viruses

Some computer viruses appear to behave like many other viruses and sometimes more than one type. These are hybrids and are called as multi-partite computer viruses.

Polymorphic Viruses

These viruses are written such that it changes its code when ever it passes to another machine so that it is difficult for an anti-virus scanner to locate them. Flaws in the program code make it easy to track down these viruses. It is usually the encryption of the code that changes every time.

Stealth Viruses

Whenever a virus attaches itself onto another file the size of the file increases and this is indicated in the File allocation table. The stealth virus uses techniques to avoid detection by redirecting the disk head to read another sector or alter the file size shown in the Directory listing .

Script Viruses

A subset of file viruses these are written in a variety of script languages like Javascript, VBS, BAT, PHP etc… They are also able to infect other file formats such as HTML (if the file format allows script execution)

ActiveX & Java Applet's

Active X and Java Controls are being used in Web browsers to enable and disable sound or video and a host of other controls. If not properly secured this is another area that virus writes use to get private data from your computer.

Many types of viruses do more than viruses do. Some are file type viruses and then a trigger may activate a code to make them behave like a worm. Therefore classification becomes difficult in these cases. The basic behavior of a virus which makes it different from a Trojan is that it replicates very fast.


We can remove all Viruses, Trojans and Worms. Call: (716) 549-5143 if you have any questions or think you have a virus.








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