This document provides an overview of computer viruses and methods for prevention and removal. It defines what a computer virus is and describes different types including boot sector viruses, file infector viruses, worms, macro viruses, and Trojan horses. Examples like Melissa and I Love You are given. Methods for manually removing some common viruses like New Folder.exe and Autorun.inf are outlined. The document stresses the importance of using antivirus software, regularly updating definitions, avoiding unsafe downloads and attachments, and making backups to help prevent and cure computer viruses.

1. PRESENTATION
ON
COMPUTER
VIRUS & ITS CURE
 Presented by:
 Md. Tamim Ahmed
ID:LL.B-052 08731
 Md. Wahidur Rahman
ID:LL.B- 052 08790

2. Content Details
 What is a virus?
 Who creates/writes viruses ?
 Type of viruses
 Major Types of Viruses
 Boot Sector Virus
 Program/File Infector
 Worms
 Macro Virus
 Trojan Horses
 Removal of Some Common Viruses
 Prevention & cure of computer viruses
 Some anti-viruses software
 Conclusion

3. What is computer virus?
 Computer viruses are a type of software program that, like a
biological virus, reproduces and spreads itself
 Some virus may display only a message on the screen,
others may slow down the Pc
 They can also erase files or even format your floppy or hard
disk and crash the system.

4. Who creates/writes viruses ?
INFO ATTACKERS
PROFIT EARNER
 VIRUS / ANTIVIRUS MARKET
PSYCHO CASES
 FOR FUN
 TO TAKE REVENG
 RELEASE ANGER

5. Type of viruses
 There are about millions of viruses present & daily 6 to 7
new viruses are found
 The following are the types of viruses:
 Boot sector Virus, Program/ File Infector, Trojan Horses,
Worms, Macro Virus, Polymorphic Virus,, Companion
Virus, FAT Virus, Logic Bombs, Spyware, Adware,
Multipartite virus, Stealth virus etc.

6. Major
Types of Viruses
Virus
Boot
Sector
Virus
Program/
File
Infector
Worms
Macro
Viruses
Trojan
Horses

7. Boot Sector Virus
The boot Sector virus affects the
booting process of the infected
computer system.

8. Program/
File Infector virus
Becomes active when the
program file carrying the virus
is opened.
usually with below extensions
.BIN .COM
.EXE .OVL
.DRV

9. Worms
 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.
 Unlike a virus, it does not need to attach itself to an
existing program. Worms always harm the network (if
only by consuming bandwidth), whereas viruses
always infect or corrupt files on a targeted computer.

10. 10
Worm Propagation
Leverage Network Connectivity

11. Macro Virus
These type of virus infects
word , excel, PowerPoint,
access and other data
files. Once infected
repairing of these files is
very much difficult.

12. Trojan horses
A Trojan horse is a program that unlike a virus
contains or installs a malicious program (sometimes
called the payload or 'trojan').
 The term is derived from the classical myth of the
Trojan Horse.
 Trojan horses may appear to be useful or interesting
programs to an unsuspecting user, but are actually
harmful when executed.
 The famous usage in hacking.

13. Trojan

14. Two examples for Viruses
 Melissa
Type : Macro virus
 I Love You
Type : worm

15. The functional logic of a
virus
 Search for a file to infect.
 Open the file to see if it is infected.
 If infected, search for another file.
 Else, infect the file.
 Return control to the host program.

16. 16
Virus
V
Virus – Needs a host

17. 17
Virus Propagation
Leverage User Connectivity

18. Cure of computer viruses

19. Removal of Some Common
Viruses
 We can remove some of the common viruses without
help of any antivirus Program.
 e.g.- New Folder.exe
 Autorun.inf ( from PDs etc)

20. New Folder.exe
 It looks just like an folder
but actually it is a .exe
file.
 Try to deleting the file.
 It will delete if you
haven’t executed it, if
you’re unable to delete
it.
 Go to Task manager ( by
pressing ctrl+shift+del )

21. Continued …
 Go to Process Tab and try
finding that the process for
the exe file and end the
process.
 Then Go to the same folder
containing the exe file and
delete it.
 Then Open Search and try
finding the .exe files of same
size and delete them all.

22. Removal of Autorun.inf
 Open Run dialog Box. Type in “CMD”
press ENTER.

23. Continued …
 The Command Prompt will Open Now. In
Command prompt go to the drive containing
Autorun.inf
 Now Type In “ attrib –h –s –a” and press enter.

24. Continued …
 This will remove drives attributes for all
Hidden, System files.
 Now Type “ Del autorun.inf” and press
ENTER.
 The Virus has been Successfully Removed.

25. Anti-Virus

26. Prevention & cure of
computer viruses
 Since virus can cause extensive effect to your
important files,possible steps must be take to
prevent attack on your pc
 If you use floppy disk to boot your pc then write
protect it
 Make backups of your impotent files in floppy or
cd and keep it in a safe place you will need it later

27. Prevention & cure of
computer viruses
 Install an Antivirus software
 Regularly update the program
 Open email attachment files only if you are
expecting the attached files, or the sender is known
and has confirmed sending the file
 Try to avoid downloading and installing software
from the Internet
 Install only registered copies of software on the
system

28. Some anti-viruses software

29. Conclusion
 I think we should not use the pc without any antivirus
security as it may cause damage to our important
data
 Do not copy or transfer any data or file without
scanning the disk.

30. Thank You !!
Any Question ??