2. At
Glance
What is Virus?
Hackers &
Crackers
Types of
Computer
Viruses
Some other
Harmful
Programs
How you
Protect your
System
against
Viruses ?
3. A virus is a program that enters the computer system
by attacking itself to another program and then
spreads itself across the system.
4. There are two different types of people who write
computer virus programs –
Hackers
Crackers
Hackers refers to the people who use their skills to enter into
computer system without authorization. Hackers are
computer enthusiasts, who break into secure systems to gain
knowledge about them and possibly use their knowledge to
play pranks.
A Cracker is malicious programmer who gain unauthorized
access to computer system for the purpose of stealing,
altering or corrupting information.
5. There are so many types of computer
viruses.
Some of them are :
Macro Virus
File Infector
Resident Virus
Network Virus
Logic Bomb
Boot Sector Virus
Multipartite Virus
Stealth Virus
6. A macro virus is a computer virus that "infects" a
Microsoft Word or similar application and causes a
sequence of actions to be performed automatically
when the application is started or something else
triggers it. Macro viruses tend to be surprising but
relatively harmless. A typical effect is the undesired
insertion of some comic text at certain points when
writing a line. A macro virus is often spread as an e-
mail virus. A well-known example in March, 1999 was
the Melissa virus virus.
7. Phrasp the most common type of virus, the file infector
takes root in a host file and then begins its operation
when the file is executed.
The virus may completely
overwrite the file that it infects, or may only replace
parts of the file. Some file infector
viruses attack
themselves to program file, usually selected .COM or
.EXE file.
8. A board virus definition applies to any
virus that inserts itself into a system’s
memory
9. A kind of virus spreads across networks in computers,
for example, Nimda and SQL SLAMMER worms are
viruses which spread over corporated networks or the
internet via e-mails.
10. A logic Bomb is a program that get executed only
when specific condition is met. The virus: Friday the
13th, , was so programmed so as to get executed on
that perticular date.
11. A boot sector virus hides in the boot sector of hard
disk. The boot sector is where your operating
system is. So every time you boot your computer
the virus gets loaded into the computer memory.
Examples of boot-sector viruses are Polyboot B,
AntiEXE.
12. This virus is spread by infected floppies and CDs.
These viruses first infect the boot sector of hard drive
and then infect the executable files stored in it. For ex.-
Ywinz.
13. These are some virus which try to hide
themselves from Anti-virus software by
resorting some tricks. Stealth virus can
safely show an anti-virus software that a
certain file is uninfected.
14. A Trojan Horse program is a file that appears
harmless unless it has executed. The Trojan Horse
program disguises itself as a game or a utility
program but when executed it can destroy the data
stored in the computer. The name Trojan Horse has
been derived from Greek mythology.
15. Worms are small pieces of software that use
computer network and security holes to replicate
itself.
Worms on the internet spread by e-mail it
searches for all the address book of the mailing
system. It then mails to all recipients.
16.
Install a good Anti-Virus software on your computer.
Update Anti-Virus regularly.
Be careful while Downloading files or programs from the
internet.
17.
Always scan your floppies, CDs, flash drives before using
them.
Do not use pirated software.
Turn on firewall of your computer operating system.
