History And Types Of Viruses Computer Science Essay

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The world of computers and information technology is going through an era of an electronic terrorism, in the form of the computer virus. It is a problem that is potentially so dangerous that it threatens the proper functioning of the virus system

History of Viruses

The computer virus was created in 1986 by two Pakistani brothers. The virus was only supposed to infect booted records and not computer hard drives like the viruses today; they are spreaded through floppy disks. It will disguise itself by displaying the uninfected boot sector on the disk. In 1987 the Lehigh virus was discovered, it was the first memory resident file infector that attached executable files and took control when a file is opened. Another virus called the Jerusalem came around the same time as the Lehigh. It too was also a memory resident but is contained bugs to reinfect programs that are already infected. In 1988, the first anti-virus was designed to detect and remove the Brain virus which is also known as the Lehigh. The anti-virus also immunized floppy disks to get rid of the Brian infection. In the late 1980's and the early 1990's, viruses on the loose which infected files and disks on the computer and caused a great deal of damage received a lot of media attention. In 1991 the Norton anti-virus software by Symantec was released. In 2000 the ILOVEYOU virus wreaked havoc around the world. This virus was created in the Philippines and was sent through email and spread around the world in one day infecting 10 percent of computers connected to the internet and causing $5.5 billion dollars in damage.

Types of Viruses

There are many types of computer viruses and sometimes it is hard to identify what type of virus it is. There are three basic types of viruses you will likely come across. Those viruses consist of the Trojan Horses, Worms, and Email viruses.

The Trojan Horses which name came from an incident that occurred in Homer's lliad. (2009, spamlaws.com). This virus is similar to how the Greeks sent an army of men, hiddedn in a wooden horse to the Trojans to get into the wall of the city just like in the poem by Homer. The Trojan hors does not reproduce it appears to be nothing more than a file on your computer. Once the virus is on your computer it allows intruders to access and read your files which makes this type of virus extremely dangerous to a computer's security and your personal privacy. You should avoid downloading from sites you are not sure of what it is or what the file or program does. Trojans comes on your computer through downloads which are installed without your knowledge. The Trojan virus is very dangerous and puts all of your information at risk even your server whether it is secure or not. The virus allows hackers to tap into your computer and steal your passwords, credit card information and all sort of important information.

Worms is software that uses computer networks and security flaws to copy or it affects other programs. The worm passes through the network to another machine that has a specific security hole. Then copies itself to the new machine and then starts it replicating process all over again.

The email virus was originally created as a word document which was uploaded by email to an internet newsgroup. Whoever opened the document and downloaded it to their computer brought something called Melissa's payload. These viruses spreads itself to the first 50 contacts in your address book and have a message attached which includes the recipient's name to make it appear to be harmless. Melissa such a powerful virus because it attacks the vulnerability that is found in the Microsoft word programming language known as VBA (Visual Basic for Application). VBA is a program language that can be programmed to perform actions such as modifying files and distributing emails (2009, spamlaws.com) Melissa was programmed by inserting a malicious code into document which was executed whenever someone opened it.

Computer Viruses

Computer viruses are self-executing, replicating programs written specifically to change the way a machine works, without the knowledge (or permission of the operator or owner). A computer virus is quite simply a type of program which is designed to make your computer breakdown. These viruses are not computer friendly and should be avoided. Whenever your computer has a virus you will experience error messages and a slowdown of the function of your computer. The viruses can impair and damage your computer. It can execute random text, audio and video messages, draining your memory, deleting your files, corrupting programs and even reformatting your hard drive.

The spreading of Viruses

Viruses spread on your computer through attachments which are sent by email. Once it is opened the virus executes itself and will begin infecting your computer, files and erasing or changing your information. Some viruses will cause little or no harm to your computer but there are some that are very dangerous and will damage your computer.

Classification of viruses

There are three classifications of viruses which are classified on the basic of their mode of existence. The three categories are boot infector, system infector, and general executable program infectors.

The boot infectors are characterized by the fact that they physically reside in the boot sector of the disk. A virus like this resides in a particular area of the disk rather then in a program file. The virus is loaded soon after Power of Self Test and control the system and remains in control at all times. Sometimes they will trap when you use (CTRL ALT DEL) and remain in control even if the system is booted from a non infected floppy and contaminating the clean floppy.

The system infectors are the second category that deals with components of the system itself. Machines need operating system in order to create an operating system if they are machines without execution.

The general executable program infectors are the third category of viruses, which are the most dangerous and devastating of the categories. The viruses changes the original program instructions to into jump mode which is its own code which follow that code with a return to the original program when executing the program the virus will load and execute then the program will follow. This virus does not leave it stays there and infect every program you execute.

Viruses Protection

Protect your computer from viruses you will need to upload and use anti-virus software programs to keep your computer secure and free of viruses. If you receive emails be sure you know the person you are receiving the emails from otherwise please delete it right away.


In conclusion beware of computer viruses which are transmitted via emails, downloading and opening attachments. Some viruses can be very dangerous and can cause serious harm to your computer. Please protection your computer by putting some sort of anti-virus software on your computer.