1) The document discusses computer viruses, how they infect systems, and their effects. It defines a computer virus as a program designed to replicate like a biological virus and harm systems. 2) Common ways viruses enter systems are through email attachments, visiting infected websites, file sharing, and downloading unauthorized software. Viruses can slow systems down, cause data loss or crashing. 3) The document outlines the history of computer viruses from 1949 to 2014, describing some of the earliest viruses like Creeper and Morris Worm. It advises using up-to-date antivirus software and practicing safe browsing and downloading habits to avoid viruses.

2. KAMRAN NASIR
REG NO:2521-SE/BSECO
2/S15
SUBJECT: COMPUTER
INSTRUCTOR: DR MOAZAM

3. COMPUTER VIRUSES

4. WHAT IS A COMPUTER VIRUS?
Think of a biological virus – the kind that makes you sick. It
persistently keeps you from functioning normally and often requires
something powerful to get of it. A computer virus is very similar.
Designed to relentlessly replicate, computer viruses infect your
programs and files, alter the way your computer operates or stop it
from working altogether. It’s estimated that the Conficker virus
infected more than 10 million computers in 2009. Tens of thousands
of computer viruses now operate over the Internet, and new
computer viruses are discovered every day.

5. HOW DOES A COMPUTER VIRUS FINDS
ME?
Even if you’re careful you can pick up computer viruses through
normal Web activities like:
1) Sharing music, files or photos with other users
2) Visiting an infected Web site
3) Opening spam email or an email attachment
4) Downloading free games, toolbars, media players and other
system utilities
5) Installing mainstream software applications without fully reading
license agreements.

6. WHAT DOES A COMPUTER VIRUS DO AND
SYMPTOMS?
Some computer viruses are programmed to harm your computer by damaging programs,
deleting files, or reformatting the hard drive. Others simply replicate themselves or flood a
network with traffic, making it impossible to perform any internet activity. Even less harmful
computer viruses can significantly disrupt your system’s performance, sapping computer
memory and causing frequent computer crashes.
Your computer may be infected if you recognize any of these malware symptoms:
1) Slow computer performance
2) Computer behavior
3) Unexplained data loss
4) Frequent computer crashes

7. COMPUTER VIRUS TYPES AND THEIR EFFECTS
( 1949-81 )
1949 – 1966 – Self-Reproducing Automata: Self-replicating programs were established in 1949, to produce a large
number of viruses, John von Neumann, whose known to be the “Father of Cybernetics”, wrote an article on the “Theory
of Self-Reproducing Automata” that was published in 1966.
1959 – Core Wars: A computer game was programmed in Bell Laboratory by Victor Vysottsky, H. Douglas McIlroy and
Robert P Morris. They named it Core Wars. In this game, infectious programs named organisms competed with the
processing time of PC.
1971 – The Creeper: Bob Thomas developed an experimental self-replicating program. It accessed through ARPANET
(The Advanced Research Projects Agency Network) and copied to a remote host systems with TENEX operating system. A
message displayed that “I’m the creeper, catch me if you can!”. Another program named Reaper was created to delete
the existing harmful program the Creaper.
1974 – Wabbit (Rabbit): This infectious program was developed to make multiple copies of itself on a computer clogging
the system reducing the performance of the computer.
1974 – 1975 – ANIMAL: John Walker developed a program called ANIMAL for the UNIVAC 1108. This was said to be a
non-malicious Trojan that is known to spread through shared tapes.

8. 1983-1998
1983 – This was the year when the term “Virus” was coined by Frederick Cohen for the computer programs that are infectious as it has the
tendency to replicate.
1986 – Brain: This is a virus also known as the “Brain boot sector”, that is compatible with IBM PC was programmed and developed by two
Pakistani programmers Basit Farooq Alvi, and his brother, Amjad Farooq Alvi.
1987- Lehigh: This virus was programmed to infect command.com files from Yale University.
Cascade: This virus is a self-encrypted file virus which was the outcome of IBM’s own antivirus product.
Jerusalem Virus: This type of virus was first detected in the city of Jerusalem. This was developed to destroy all files in an infected
computers on the thirteenth day that falls on a Friday.
1988 – The Morris Worm: This type of worm was created by Robert Tappan Morris to infect DEC VAX and Sun machines running BSD UNIX
through the Internet. This is best known for exploiting the computers that are prone to buffer overflow vulnerabilities.
1990 - Symantec launched one of the first antivirus programs called the Norton Antivirus, to fight against the infectious viruses. The first
family of polymorphic virus called the Chameleon was developed by Ralf Burger.
1995 – Concept: This virus name Concept was created to spread and attack Microsoft Word documents.
1996 – A macro virus known as Laroux was developed to infect Microsoft Excel Documents, A virus named Baza was developed to infect
Windows 95 and Virus named Staog was created to infect Linux.
1998 – CIH Virus: The release of the first version of CIH viruses developed by Chen Ing Hau from Taiwan.

9. 1999-2014
1999 – Happy99: This type of worm was developed to attach itself to emails with a message Happy New Year. Outlook
Express and Internet Explorer on Windows 95 and 98 were affected.
2000 – ILOVEYOU: The virus is capable of deleting files in JPEGs, MP2, or MP3 formats.
2001 – Anna Kournikova: This virus was spread by emails to the contacts in the compromised address book of Microsoft
Outlook. The emails purported to contain pictures of the very attractive female tennis player, but in fact hid a malicious
virus.
2002 – LFM-926: This virus was developed to infect Shockware Flash files.
Beast or RAT: This is backdoor Trojan horse and is capable of infecting all versions of Windows OS.
2004 – MyDoom: This infectious worm also called the Novang. This was developed to share files and permits hackers to
access to infected computers. It is known as the fastest mailer worm.
2005 – Samy XXA: This type of virus was developed to spread faster and it is known to infect the Windows family.
2006 – OSX/Leap-A: This was the first ever known malware discovered against Mac OS X.
Nyxem: This type of worm was created to spread by mass-mailing, destroying Microsoft Office files.
2007 – Storm Worm: This was a fast spreading email spamming threat against Microsoft systems that compromised
millions of systems.
Zeus: This is a type of Trojan that infects used capture login credentials from banking web sites and commit financial
fraud.
2008 – Koobface: This virus was developed and created to target Facebook and MySpace users.

10. HOW TO AVOID VIRUSES?
ANTIVIRUS OR ANTI-VIRUS SOFTWARE (OFTEN ABBREVIATED AS AV), SOMETIMES KNOWN AS
ANTI-MALWARE SOFTWARE, IS COMPUTER SOFTWARE USED TO PREVENT, DETECT AND REMOVE
MALICIOUS SOFTWARE.

11. COMPUTER VIRUS HELP
Make sure that you have the best security software products installed
on your computer:
1) Use antivirus protection and a firewall
2) Get antispyware software
3) Always keep your antivirus protection and antispyware software
up-to-date
4) Update your operating system regularly
5) Increase your browser security settings
6) Avoid questionable Web sites
7) Only download software from sites you trust. Carefully evaluate
free software and file-sharing applications before downloading

12. QUERY? Feel free to ask.