At Glance

What is Virus?

Hackers & Crackers

Types of Computer Viruses

Some other Harmful

Programs

How you Protect your

System against

Viruses ?

A virus is a program that enters the computer system by attacking itself to

another program and then spreads itself across the system.

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.

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

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.

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.

A board virus definition applies to any

virus that inserts itself into a system’s

memory

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.

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.

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.

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.

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.

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.

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.

Install a good Anti-Virus software on your computer.

Update Anti-Virus regularly.

Be careful while Downloading files or programs from the

internet.

Always scan your floppies, CDs, flash drives before using

them.

Do not use pirated software.

Turn on firewall of your computer operating system.

Presented

By:

Guided By : Vandana Ma’am