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In a computer system virus does not evolve by itself it is uploaded or in ected in a network or into a storage
media. It is communicable i.e. it is transmitted from one computer to another computer or to a network by
some medium of transmission like pen drive external hard disk software internet connection bluetooth
etc. hen infected viruses replicate by themselves.
here are different types of viruses that infect specific components or specific functioning of a computer
system. hey can range in severity. Some may cause mild damages while others can cause severe damages
to hardware software or files. xamples of some common viruses are i ryte OneInstaller oobface ia oor
rO c yte andit rain Small. Stealth etc.
Boot Sector Virus
ooting is the process of loading operating system in the primary memory from the boot sector. oot sector is the
core area of hard disk storage where the most important programs like OS are stored.
boot sector virus gains complete control over the Master oot ecord M . M is the first sector of the
computer hard drive that stores the information about loading the operating system into the main memory.
oot sector virus replaces the location and information of the operating system in order to stop it from
getting loaded into the main memory resulting into errors during booting. Michelangelo olyboot. Stones
and nti are some common examples of boot sector virus.
Program File Virus
program file infecting virus is a type of malware that infects the executable files of a program with the
intention of causing permanent damage or making the program useless. file infecting virus overwrites
the code or inserts infected code into the source of an executable or program file. hen such programs are
executed such virus activates and damages the files. hen a program runs many times program viruses
are deliberately loaded in a program by the developer. program file infecting virus is also known as a File
In ector . Sunday and ascade are the common examples of program file viruses.
Worms
orms are the computer programs or algorithms which are alien to the host computer and are designed to
purposely slow down the functioning of a computer. orms replicate inside the system and thus occupy a huge
memory space in the storage device. orms spread more commonly in computers that are connected to a
network. xamples of worms are inux allpit Morris worm Nimda worm Mydoom Sasser etc.
Trojan Horse
ro ans are infectious programs which silently infect the computer and corrupt the files of a host computer.
Such programs often accompany computer games but unlike worms they don t replicate themselves. hey
are activated when the user is busy interacting with the entertaining programs or with interface like computer
games. Some examples of ro an are inux ifatch Infostealer. ronbank etc.
ro an orses are often used by hackers as they can enter into the database of a computer system under the
guise of some entertaining package. he term backdoor is often used for tro an horse. he user interacts
with the program and simultaneously the infection takes place behind the interactive interface. Once a tro an
horse has infected a computer system it becomes easier for a hacker to access it remotely and perform
unethical operations and steal important information from the infected computer.
o prevent a ro an orse virus from entering and infecting a computer it is advisable not to open spams
email attachments or files that may look attractive and luring but have been sent by unknown senders on the
Internet.
Information Technology and Communication 5

