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Classification of Viruses

Viruses are classified on the basis of their mode of existence and there are three categories of viruses:-
  • Boot Infectors:- A system infected by such virus wil have the virus residing in a particular area of the disk rather in a program file. This virus get loaded soon after the Power on self Test and control the system and remains in control at all times. Boot infectors create “bad sectors”.
  • System Infectors:- This category of virus deals with the components of the system itself. System infectors attach themselves to a file such as COMMAND.COM or other memory resident files and manipulate these files. System infectors differ from boot infectors that system infectors gain control after the computer is booted and infects a hard disk or bootable floppies which contain system files only. 
  • General Executable Program infectors:- This type of viruses are most dangerous virus. They attach themselves to a program files and can spread to almost any executable program in any system. This viruses change original program instruction. As a result, whenever the program is executed, the virus gets loaded and executed first and then allows the original program to proceed.

Different types of Virus

  • Brain Virus:- This is the first developed virus, also known as Pakistani virus. It was developed by Pakistani brothers. The virus pops up screen saying “welcome to the Dungeon”. This virus is known to destroy data and are highly contiguous.
  • Scores Virus:- Score virus has a built in time trigger that activates at 2,3,4, and seven days after the disk has infected. Data files are not directly affected by this virus, but ensure of this virus requires deletion of all files.
  • Lehigh Virus:- This virus originated at the Lehigh University computer centre. This virus stays in the stack space of COMMAND.COM. With the booting of a PC from an infected disk, the virus is spread through commands such as COPY, TYPE, DIR etc. The boot sector and FAT get ruined from this virus.
  • Friday the 13th:- This virus attack not only COMMAND.COM but also other executable files. When a .COM or .EXE file is executed for the first time after booting, the virus captures a specific interrupt and inserts its own code. It increases the .EXE and .COM file size cause the program to become too large in loaded into the memory
  • SunnyVale Slug Virus:- This virus display a message “ Greetings from SunnyVale. Can u find me?”. And also modifies the COPY command resulting in deletion of files instead of copying.
  • Raindrops Virus:- This virus infects .COM files. It intercepts the load and execute function of MS-DOS. It checks whether the file is .EXE or not, if the file is not an EXE file, the fist three bytes of the file are replaced by a jump instruction at the end of the file, where it gets attached after encryption. This results in dropping or showering of characters on the screen like raindrops with sounds.
  • Happy Birthday 30th:- This virus gets activated on January 5th. If any of the program get executed, and will ask the user to type “Happy Birthday 30th”. It can destroy all the data on the disk. 
  • Key Logger:- A Key logger is a software program designed to record every key stroke on the machine. Its purpose is usually to allow the user of this tool to gain access to confidential information typed on the affected machine, such as a user's password or other private data.
  • Password cracking:- Password cracking is the process of recovering passwords from data that has been stored in or transmitted by a computer system. A common approach is to repeatedly try guesses for the password.
  • Packet sniffer:- A packet sniffer is an application that captures data packets, which can be used to capture passwords and other data in transit over the network.
  • Spoofing attack (Phishing):- A spoofing attack involves one program, system, or website successfully masquerading as another by falsifying data and thereby being treated as a trusted system by a user or another program. The purpose of this is usually to fool programs, systems, or users into revealing confidential information, such as user names and passwords, to the attacker.
  • Rootkit:- A rootkit is designed to conceal the compromise of a computer's security, and can represent any of a set of programs which work to subvert control of an operating system from its legitimate operators. Rootkits may include replacements for system binaries so that it becomes impossible for the legitimate user to detect the presence of the intruder on the system by looking at process tables.

Important Point

  • Wikipedia introduced by jimmy wales in jan 15, 2001.
  • YouTube launched by Javed Karim, Chad Hurely, Steve Chen in Feb 15, 2005
  • The Pandora internet radio service is launched in Aug 25, 2005.
  • Bing launched by Microsoft as search engine in June 3, 2009.
  • Google:- It was first incorporated as a privately held company on September 4, 1998. Founder:- Sergey Brin and Larry Page.
  • Yahoo:- (Yet Another hierarchical Officious Oracle) started in Jan 1994 by Jerry Yang and David Fillo.

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