computer virus

Introduction about computer virus for students

History Of Virus

The possibility of self-replicating code was discussed among scientists as early as the 1960’s and the first known example was demonstrated at Xerox Corporation in 1974.
Dr. Frederick Cohen began research on actual computer viruses in 1983 at the University of Southern California and subsequently warnings concerning the potential widespread virus epidemics were made.

The University of California at Los Angeles received funding from IBM Corporation and the National Science Foundation also researched about computer viruses.
VIRUS ORIGIN PAKISTANI (also called Brain) University of Delaware
LEHIGH (also called COMMAND.COM) Lehigh University
FRIDAY THE 13TH (also called April Fool) Hebrew University in Jerusalem
CHRISTMAS (also called Christmas Card or Christmas Tree) virus West Germany
The Pakistani, Lehigh, Friday the 13th viruses spread primarily from infected computers that were shared within University libraries and computer laboratories.
Many students unknowingly carried infected diskettes from the lab to their own computers and back again, causing campus wide epidemics that were very difficult to eradicate.
The Christmas Virus was actually an electronic chain letter that sent duplicates of itself through the worldwide Vitnet electronic mail system, from its origin in West Germany, this fast-multiplying “Merry Christmas” message spread over five continents, and within a few days had swamped the IBM electronic mail system.

How Does a Virus Works?

Most viruses are written in an assembler or machine code to remain fast and small, and thereby elusive; however, viruses can be written in any programming language that supports file manipulation; even batch and macro languages commonly used within spreadsheets and other software products can support virus like activity.
Viruses usually attach themselves to other executable files or inside the operating system.
As a virus must be run to do its work, one that resides in the operating system is usually a more serious threat because it can be continually active and continually watching for opportunities to infect or attack.
An executable file vim’s typically appends a copy of itself to the beginning of another program.
When the program is run, the virus runs first, attempts to infect another program, and then passes control to the usually sees nothing wrong except possibly a run-the time it takes the virus to infect another program.

Why Are Viruses Written?

Many viruses show evidence of having been “hacked” or modified by a number of different people over a period. In many cases, what was originally a harmless virus is turned into a dangerous virus.
Many viruses are designed only to infect and contain no intentionally destructive logic. They appear to have been created out of curiosity, for the intellectual challenge, or even as instructor-authorized programming projects in school (an unwise exercise).
Some viruses are designed from the start as destructive weapons. Motives for their development and/or intentional introduction into a system may include thrill seeking, political aims or revenge against an employer, co-worker, industry, government agency, or the society as whole.
Safety Precautions to Prevent Infections:
1. Avoid borrowing diskettes from other sources especially from your classmates. Avoid using programs of others.
2. Refrain from using other system disks for booting up your computer.
3. Label your disk properly.
4. All system programs like DOS, WS, LOTUS 123 must be write-protected.
5. Use a virus detection and removal utility software regularly.
6. Check all new programs or software you buy before using.
7. Back up all your data files.8. Do not allow others to run their programs on your PC.