A computer virus is a program that spreads from one computer to another and interferes with computer operation. Viruses can corrupt or delete data. They replicate by attaching themselves to other programs or files. Common types include macro, polymorphic, and metamorphic viruses. Symptoms of a virus include slow performance, random restarts, and loss of disk space. Viruses are typically spread through email attachments, networks, removable media, and pirated software. People create viruses for fun, profit, or revenge, while info attackers aim to disrupt networks. To protect against viruses, users should install and regularly update antivirus software, avoid unknown emails/files, and use security measures like firewalls.

1. COMPUTER
VIRUSES

2. WHAT IS A COMPUTER
VIRUS?
A computer virus is a small software program that spreads from one computer to
another computer and that interferes with computer operation. A computer virus
may corrupt or delete data on a computer, use an e-mail program to spread the
virus to other computers, or even delete everything on the hard disk.
.
CHARACTERISTICS OF A COMPUTER VIRUS:
 the ability to replicate itself.
 the ability to attach itself to another computer file.

3. WORKING OF COMPUTER
VIRUS
A Computer Virus needs another program in order to be able to
be activated and infect other computers files.
For example, a virus might attach itself to a spreadsheet
program. Each time the program runs, the virus runs too.
A file containing virus is called infested file.

4. TYPES OF COMPUTER VIRUSES
 Stealth viruses
Use certain techniques to avoid detection.
 Macro Viruses
Infects the macros within a document or template.
 Polymorphic viruses
Encrypt its code in different ways
 Metamorphic viruses
Rewrite themselves each time
they infect a new file.

5. TYPES OF COMPUTER VIRUSES
 Boot viruses
Affects boot sector of a floppy or hard disk.
 Program viruses
Infect executable program files.
 Multipartite viruses
A hybrid of Boot and Program viruses.
 Directory Virus
Directory viruses change the paths
that indicate the location of a file

7. TROJAN HORSE
Covert
Leaks information
Usually does not reproduce

8. WORMS
Spread over network connection
Worms replicate
First worm released on the Internet was called
Morris worm, it was released on Nov 2, 1988.

9. WHAT CAN VIRUSES DO?
 Format hard disk
 Copy, rename and delete files
 Modify files dates and extensions
 Display false message every few times
 Damage data
 Damage software

10. SYMPTOMS
 Computer runs slowly
 Random restarts
 Unknown and uninstalled icons on desktop
 Icons change in appearance
 System memory and disk space is reduced
 New windows open up at an alarming rate
 Error messages on regular basis
 Files mysteriously disappear

11. HOW VIRUS SPREADS?
 Email
Opening and downloading an email containing virus
 Networks
Connecting with network that contains virus
 Removable Storage Media
Floppy discs, CDs and flash devices
 Pirated Software
Installing pirated software that contains virus

12. W H O C R E A T E S V I RU S E S A N D W H Y ?
Common people:
 For fun
 Release anger
 Take revenge
 For fame
Profit earners:
 Antivirus market
Info attackers:
 Disrupt enemy’s information and network

13. HOW TO PROTECT FROM
VIRUS?
 Latest antivirus should be installed
 Antivirus software must be upgraded regularly
 Unknown emails should not be opened
 Unauthorized software should not be installed
 Removable storage media should be scanned
 Freeware and shareware software from internet should be checked
before installing

14. TOP SEVEN ANTIVIRAL
PROGRAMS
Kaspersky Antivirus
 Avira Antivirus
Mcafee Antivirus
Symantec Norton Antivirus
Bit Defender 2010
Quick Heal Antivirus
AVG Antivirus

15. GENERAL SECURITY TIPS
 Apply user-level security on file sharing when
needed.
 Don't open email attachments from unknown
senders.
 Use Rich Text Format files instead of Word
Documents.
 Updated anti-virus program
 Set the BIOS boot sequence
 Write protection