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A boot sector virus gains complete control over the Master Boot Record (MBR). MBR is the first sector of the
computer hard drive that stores the information about loading the operating system into the main memory.
Boot Sector virus replaces the location and information of the Operating System in order to stop it from
getting loaded into main memory resulting into errors during booting.Michelangelo, Polyboot.B, Stoned
and AntiEXE are some common examples of boot sector virus.
Program File Virus
A 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. A file-infecting virus overwrites
the code or inserts infected code into the source of an executable or program file. When such programs
are executed, such virus is activated and damages the files. When a program is run repeatedly, program
viruses are deliberately loaded in a program by the developer. A program file infecting virus is also known
as a File Injector. Sunday and Cascade are the common examples of program viruses.
Do you know?
Creeper is the first computer virus that displays “I’m the creeper, catch me if you can!” in 1971 by Bob
Thomas. It was just a test to check if self-copy of a program was possible.
Worms
Worms 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. Worms replicate inside the system and thus
occupy a huge memory space in the storage device. Worms spread more commonly in computers that
are connected on network. Examples of worms are Linux. Ballpit, B!gen3, Morris worm, W32/Nimda worm,
Mydoom, Sasser etc.
Trojan Horse
Trojans 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.
They are active inside the computer when the user is busy interacting with the entertaining programs or
with interface like computer games. Some examples of Trojan are Linux.Wifatch, Infostealer.Kronbank, etc.
Trojan Horses are often used by hackers as they can enter into the database of a computer system under
the guise of some entertaining package. The term “backdoor” is often used for trojan horse. The user
interacts with the program and simultaneously the infection takes place behind the interactive interface.
Once a trojan 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.
To prevent a Trojan Horse virus from entering and infecting a computer, it is advisable not to open
spams, e-mail attachments or files that may look attractive and luring but have been sent by unknown
senders on the Internet.
Ransomware
Ransomware is a type of malware that encrypts files or locks a system, demanding a ransom for data
recovery. It spreads through phishing emails, malicious downloads, or security vulnerabilities. Once
infected, users lose access to their files until they pay the ransom, though payment does not guarantee
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