This article is presented by:Dick Steflik

Viruses & Worms

A Couple of Definitions
A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user.
“a program that replicates by “infecting” other programs, so that they contain a copy of the virus”

How

Viral code is attached or “inserted” into the order of execution so that when the legitimate code is run the viral code is also run or run instead of the legitimate code.
May be “tacked” on to the end of an executable file or inserted into unused program space.
Legitimate code must be modified so that the viral code is branched/vectored to.
Most viruses
Do not damage the original program or damage the hardware
May damage data files
“trash” firmware
Mess up boot records
But, some do
For this reason most can be cleaned up with anti-virus software.

The Normal Virus works like this

User call for a legitimate program
The virus code, having inserted itself in the order of execution, executes instead or in addition to the legitimate program.
The virus code terminates and returns control to the legitimate program
For more information about this article,please follow the link:

http://cs.binghamton.edu/~steflik/cs455/..._Worms.ppt