Computer viruses are malicious code that replicates by copying itself to other programs and can change computer performance. Viruses require user permission to spread. Some famous viruses include I Love You, Cryptolocker, and MyDoom. Viruses spread by sharing infected files, visiting infected websites, opening spam emails or attachments, downloading unverified programs, and failing to read software license agreements fully. Symptoms of viruses include slow performance, erratic behavior, data loss, and frequent crashes. Protection methods include not opening suspicious messages, deleting spam, updating the OS regularly, using antivirus software, and only downloading from trusted sites.

1. COMPUTER VIRUS
BY: DIKSHYANTA DHUNGANA
TO: PRABIN DAHAL

2. INTRODUCTION ON
COMPUTER SECURITY
• Malicious code which replicates by copying itself to
another program.
• It change computer performance.
• Required permission of user to spread.
• Worm is a stand alone programming which don’t
require any hosting
• Both virus and worn are referred as malware.

3. SOME FAMOUS VIRUS
• I love you virus is one of the most well-known and destructive
virus of all time which used same style of Melissa virus.
• Cryptolocker is also on of the most popular malware which is
attached with email and encrypted the file so user cant access
them.
• MyDoom spammed junk mail through infected computers, with
text that said ” Andy I’m just doing my job, sorry nothing
personal.
• Many others famous virus are there some are: Slammer, Anna
Kournikova, Stuxnet

4. TYPES OF VIRUS
• Trojan Horse: It is a program that causes unexpected effects when willing installed or run by an
unsuspecting user. It is generally deeply buried in the code of the target program and lie dormant for
specified period. It is also useful program but inside it crash the computer, download third party
application and delete files and folders.
• Virus: Virus is a code segment, which replicates by attaching copies to existing executables. Viruses
are currently designed to attack single platforms. A platform is defined as the combination of
hardware.
• Worm: A “worm” is a program that travels independently along computer cables. It spread copies of
itself through a network. Most computers are connected via cabling, so these can do a lot of damage
in a short time.
• Trapdoors: A trapdoor is a secret, undocumented entry point into a module. In other words, it is a
feature in a program by which someone can access the program other than by obvious, direct call,
perhaps with special privileges.
• Logic Bomb: A “logic bomb” is a program that sits on your computer and does nothing, until…. The
‘until’ could be pressing a key, like the ESC key.

5. HOW DOES VIRUS FIND VICTIM?
• Sharing music, files or photos with other users.
• Visiting an infected Web site.
• Opening spam email or an email attachment.
• Downloading free games, toolbars, media players and other
system utilities.
• Installing mainstream software applications without fully
reading license agreements.

6. WHY VIRUS ARE CREATED ?
• For money
• For revenge
• An Ego
• Stealth

7. SYMPTOMS OF COMPUTER
VIRUS
• Slow performance
• Erratic computer behavior
• Unexplained data loss
• Frequent computer crashes

8. PROTECTION FROM VIRUS
• Don’t open messages from unknown senders.
• Delete the message you suspects to be spam.
• Update OS regularly
• Increase browser security setting
• Get antispyware software
• Only download from trusted sites.