The presentation deals with the computer viruses and types

1. Computer VirusComputer Virus
ByBy
Dr. Pravin H. GhosekarDr. Pravin H. Ghosekar
M.Sc.(C/S), MCM, DBM, M.Phil(IT), M.Phil(Comm), MBA, BJ. Ph.D.M.Sc.(C/S), MCM, DBM, M.Phil(IT), M.Phil(Comm), MBA, BJ. Ph.D.
HOD Computer DepartmentHOD Computer Department
Dhanwate National CollegeDhanwate National College
NagpurNagpur
08/10/201008/10/2010

2. Virus
• A Computer virus is a program (mostly written in
Assembly language) that can copy itself and infect
a computer without permission or knowledge of the
user.
• The virus program lies hidden and attacks
surprisingly to a host, replicates and infects new
hosts.
• A virus acts according to instructions written in
the program.
• The virus may modify or copies themselves, as
occurs in a biological virus.
• Some viruses are programmed to damage the
computer by damaging programs, deleting files, or
reformatting the hard disk. Other virus programs
simply replicate themselves and make their
presence known by presenting text, video, or audio

3. Virus
The first PC virus ‘Brain Virus’ was discovered (and created)
in 1986 by two Pakistani Brothers at Lahore. Some of the
popular viruses are :
• Brain
• Disk Washer
• Stone
• Jerusalem
• DIR II
• Dark Avenger
• Joshi
• Raindrop
• DieHard
• I Love you
• W32
• PWS-LegMir
•

4. Types of Virus
• Partition Table / Boot sector viruses
• When the computer is booted, control comes to
the first physical sector of a disk, which
contains a very tiny code that loads in a
partition table and passes control to the boot
sector.
• In a disk having a boot sector virus, the first
instruction in the boot sector is changed so
that it points to the area where the virus is
located.
• Hence when the computer is booted with a boot
sector virus, the virus gets into the system
before Operating System

5. Types of Virus
File Viruses
• These viruses do not infect the boot sector
partition table but they infect the executable
files ( i.e. EXE and COM extension files and
sometimes even overlay files i.e. OV/OVR
extension )
• These viruses get themselves attached at the
beginning or the end of an executable file
System Infectors
• The System Infector Viruses enter the system
though device driver files. These viruses get
attached to various parts of the operating
system.
• It may attract on IO.SYS, MSDOS.SYS and
COMMAND.COM.

6. Trojan Horses
• In computers, a Trojan horse is a program in which
malicious or harmful code is contained inside harmless
program or data in such a way that it can get control and
do its chosen form of damage, such as damaging the file
allocation table on our hard disk.
• The term comes from Greek mythology about the Trojan
War. According to legend, the Greeks presented the
citizens of Troy with a large wooden horse in which they
had secretly hidden their warriors. During the night, the
warriors emerged from the wooden horse and overran the
city.
• Trojan horses are the very common and are found mostly
on Computer Bulletin Boards.
• Trojans are used and appears to perform a desirable
function but it performs undisclosed malicious functions.
For eg. Waterfalls.scr

7. WORM
• A computer worm is a self-replicating computer
program.
• It uses a network to send copies of itself to
other nodes (computer terminals on the
network) and it may do so without any user
intervention.
• Worms almost always cause harm to the
network, if only by consuming bandwidth,
whereas viruses almost always corrupt or
modify files on a targeted computer.
• Worms may cause harm to a computer system's
hosted data, functional performance, or
networking throughput, when executed.
For. Ex. Morris Worm, Mydoom, ExploreZip

8. SPYWARE
• Spyware is computer software that is
installed secretly on a personal computer
to intercept or take partial control over
the computer, without the user's
knowledge.
• Spyware is a software that secretly
monitors the user's behavior, and
perform activities for financial or
personal gain
Ex. Cool WebSearch, Internet Optimizer, Zango,
HuntBar, Movieland,etc.

9. Antivirus
• Antivirus softwares are computer programs
that attempt to identify, neutralize or eliminate
malicious software.
• The term "antivirus" is used to combat a wide
range of threats, including virus, worms, trojan
horses and other malware.
• Antivirus software can monitor our system for
any virus attack from the outside world viz.
Internet, floppy, CD, USB, etc. during
downloading/copying of files.
• It can also detect and take action if virus is
found on a disk.
Eg. QuickHeal, AVG, Avira, Nortan, eScan, FSecure, NP etc.

10. Anti Spy virus
• In response to the emergence of spyware,
Antispyware are develop to protect computer
from spyware attack.
• An anti spyware program can protect our
computer against spyware. There are numbers
of anti spyware softwares that are available on
the Internet.
• Most of the antispyware softwares are
available free on the Internet. But these free
anti spyware can even harm our system; they
may be virus or spyware itself. Before using any
free anti spyware we need to check the
reliability of this software.

11. Firewall
• A firewall is a device or set of devices configured
to permit, deny, encrypt all computer traffic
between different security area based upon a set
of rules and other criteria.
• A firewall's basic task is to regulate some of the
flow of traffic between computer networks of
different trust levels.
• It prevents unauthorized users on the Internet
from reading the files and programs on the LAN.
• Users behind firewall can access Internet services,
but can’t provide them or intranet services to
others outside the firewall. Using firewall, we can
also restrict users from visiting to the specific
sites.

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