Done by Vandana P Computer Virus A computer

Done by: Vandana. P.

Computer Virus A computer virus is a destructive software program. It is a program that is secretly put on to a computer in order to destroy the information that is stored in it. How does it spread • Spreads through disks, networks, email links etc. • Is inactive until you have executed an infected program or application.

What a Virus cannot do • Cannot infect write – protected discs or written documents. • No Virus can do a physical damage to computer hardware. The Creeper was the first Virus that was detected, on ARPANET, in the early 1970 s.

Symptoms of a computer virus • The computer runs slower than usual. • The computer stops responding/ locks up frequently. • The computer crashes, and then it restarts every few minutes. • Applications on the computer do not work correctly. • Disks or disk drives are inaccessible. • You see unusual error messages. • You see distorted menus and dialog boxes. • You cannot print items correctly. • New icons appear on the desktop. • A program disappears from the computer even though you did not intentionally remove the program.

Types of computer viruses depending thethe infection methods. 1. - classified Boot Sector virus – Itupon affects boot sector of a computer. Damage caused • The virus is loaded into the memory when the computer is turned on. • It then infects boot sectors on floppies or other removable media. Remedy • Ensure that floppy disks are write – protected. The first PC virus was a boot sector Examples virus named Brain, created in 1986 • Polyboot. B by the Farooq Alvi Brothers. • Form • Disk Killer • Michelangelo • Stoned

2. File infector virus – It infects the files containing executable codes like. exe, . com, . dll, . bin, . sys and many more files. Damage caused • The virus will stay in memory and continue to infect other programs. • It permanently destroys the content of these files. Remedy • Ensure that the files affected are deleted. Examples • Jerusalem • Cascade

3. Macro computer virus – It infects the macro files. [ Macro is a set of commands written by the user in MS Word, Excel Access etc. , to be executed later. ] Damage caused • Whenever any macro is executed the virus show their effect by altering the macro code. • Some macro virus replace command names like save, open etc. with their code. • The virus can copy itself to other files and even delete files. Remedy • Use the command ‘Disabe. Auto. Macros’ in any macro that is written. • Hold down the shift key while opening a document. Examples • W 97 M. Melissa • WM. Nice. Day • W 97 M. Groov

4. Multipartite virus – Some computer viruses appear to behave like many other viruses and sometimes more than one type. These are hybrids and are called as multipartite virus. Damage caused • The virus infects boot records and program files. Remedy • Particularly difficult to repair. Examples • One_Half • Emperor • Anthrax • Tequilla

5. Polymorphic virus – This virus changes its code whenever it passes to another machine. Remedy • Difficult for an anti-virus scanner to locate them. .

WORMS They are destructive software programs designed to spread through computer networks. Attack: • By opening an e-mail attachment or message that contains executable scripts. They replicate themselves from system to system without the use of a host file, and can lead to negative effects on your system. • They easily penetrate most firewalls and other network security systems. Examples • Sasser worm • Blaster worm • Conficker worm •

TROJAN HORSES They claim to be something friendly, but contain malicious code. The code when triggered causes loss or even theft of data. They do not replicate. Attack: • By opening an e-mail attachment. • When you download and run a file from the Internet. Examples • Trojan. Vundo

LOGIC BOMBS A destructive program which lies dormant until a specific piece of program logic is activated. They do not replicate. Their objective is to destroy data on the computer once certain conditions have been met.

Who am I? 1. I can infect files that contain executable codes. File Infector virus 2. I know how to be like many other viruses and am a hybrid virus. I can infect both boot records and program files. Multipartite virus 3. I am a destructive software program designed to spread through computer networks. Worms 4. My name resembles an animal. I contain malicious codes. I aim at causing loss, or even theft of data. Trojan Horse

Using an anti-virus software Ø Used to prevent, detect and remove destructive programs, including computer virus, worms and Trojan horses. Ø Can be set to automatically scan • Diskettes when inserted into the disk drive • Files when downloaded from the Internet • emails when received. Ø Some anti-virus software can be availed for free and some have to be bought.

Some famous antivirus softwares are: Ø Norton anti virus Ø Mc. Afee Virus scan Ø Kaspersky Virus scan

Ø Panda Ø PC Tools Ø Quick Heal etc.

HAPPY COMPUTING !!!