A computer virus is basically a program written for destructive purpose. It is written in such a way that it can enter the Computer without the knowledge of the machine or the user. It enters the machine through an infected Pen Drive/CD/ Memory Chip/ Internet/Network (LAN or WAN) or a program. It has the capability to make perfect copies of itself and cause abnormal functioning of the machine.
A computer virus is a program and should not be confused with the biological virus which is an organism, however both of them have a number of common features as far as their activities are concerned.
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| Computer Virus |
A computer virus and the biological virus are similar in the following respects:
- Both have the capability to replicate themselves and hence spread.
- Both need a carrier to get into the system. The computer virus uses a program or an infected Pen Drive/HDD/CD/Memory Chip/ Internet/Networks (LAN or WAN) to get into the machine.
- Both are parasite's, the computer virus is a parasite on the computer system it uses the computers resources like memory (work space in which the computer works) and the programs to replicate itself, it also spreads to other Pen Drive/HDD/CD/Memory Chip/ Internet/Networks (LAN or WAN) used on a infected machine.
- Both replicate to such an extent that they finally destroy the carrier used and the other programs/ cells. The computer virus destroys the programs and data on the system.
The major difference between the two is that a biological virus causes physical harm to the organism attacked whereas the computer virus does not cause any physical damage to the system. (Although some virus are written to cause damage to particular parts of system. some viruses unintentionally cause damage to the system). But The harm caused by the Computer virus to the data/programs stored in it is even greater. The Computer is mainly used to store and manipulate data or information. Thus the loss of information gathered over a span of time or programs developed after a considerable research and development cost can be disastrous.
Origin of Virus
The idea of Viruses started with the possibility of writing self replicating software. This idea was first put forward in 1950 by John Von Neuman. At that time, most of the programmers except a few at AT&T rejected it as absurd. These few programmers at AT&T worked on it as a recreational game after office hours. Each would write code that would destroy other programmers code ( which was out to destroy their code) in the memory, the winner would be the person with the maximum number of live code.
The game was strictly kept within the AT&T premises and was never divulged outside for its destructive potentials's.
It was Ken Thompson, Co-author or UNIX who while receiving an award disclosed about the existence of such an game, he also asked programmers to try and write such programs. This was the beginning, and within a short time viruses emerged that destroyed data.
Early viruses were brain work of hackers who derived tremendous satisfaction with the fact of entering others systems. Such viruses would flash some message or suspend the users task and make him perform some silly task like type in Happy Birthday or Shanskar's Virus. When opening or closing a Word document, a dialogue box pops up displaying the string text "Did you wish Shankar on his birthday?". In due course complex algorithms were developed that would cause maximum damage to the infected system. For, example the virus would erase all information on the user's machine only after the information stored is more than half the maximum capacity.
Illegal copying of software gave a major boost to the development of viruses. Software developers whose software was widely pirated, and who got little returns for their efforts, would circulate infected copies of software to teach a lesson to the users of pirated software.
Virus Activities
The first and the foremost objective of a typical virus is to replicate itself and hence to spread to as many programs as possible.
Another important objective of a virus is to destroy data or programs by overwriting parts of data or program or by simply erasing them.
Other objectives of a virus are to cause some sort of malfunctioning of the Computer System.
The virus can cause the malfunctioning of the computer in a number of ways and it differs from virus to virus. The malfunctioning caused could be :
- To decrease the speed of operation of the Computer.
- To disorganize the data/program (deletion of File Allocation Table (FAT) or New Technology File System (NTFS).
- To decrease the memory (space in which the Computer works), and also decrease the storage of the computer.
- To cause strange movements and patterns on the screen, thereby making it impossible to work on the machine.
To understand how the virus causes malfunctioning of the computer it is important to understand the normal functioning of the computer and the way in which the computer stores information and retrieves it from the storage devices.
How Do Virus Spread?
The spread of virus to systems is mainly through the use of Internet/Networks (LAN or WAN) and in other ways infected Pen Drive/HDD/CD/ Memory Chip etc. A system can get infected by running infected programs, by starting a system (booting) with a infected Pen Drive/CD/ Floppy, Memory Chip etc or by sharing of infected programs or data over Computer networks.
The virus copies itself on the following way infected Pen Drive/Floppy/CD/ Memory Chip and Internet/Networks used on the system. The virus copies onto the boot record if it is a Boot sector virus or onto the executable files like .COM and .EXE files.
Note : If you use Internet, must installed original licensed version Anti-virus in your Computer system. Because, if you download the Software, Games and Apps in your system without using original version Anti-virus, It is dangerous for your Computer software or data including hardware.
Symptoms of a Virus Attack:
- Frequent hanging of the system, that is the system stops functioning.
- Decrease in the main memory ( The space in which the computer works), causing problems when executing large programs.
- Decrease in the free space available on the Pen Drive , HDD (Hard Disk Drive). This is because of increase in the size of the infected files.
- Loss of parts of files. This may be because of partial destruction of the File System like (FAT/NTFS etc.) File Allocation Table/ New Technology File System.
- Deletion of a file or a number of files from the diskette. This may be due to partial destruction of Root directory.
- Dramatic decrease in the speed of the system. This may be either due to increase in the time taken to access Pen Drive/HDD/CD etc. or due to virus executing itself between the program.
- Appearance of strange message or strange patterns on the screen.
It should however be noted that this could also happen due to other reasons and the presence of virus should be ascertained using some virus detecting Software.
List of computer viruses
- The ILOVEYOU (Love Bug) virus is considered one of the most virulent computer virus ever created and it's not hard to see why. Code Red. Code Red first surfaced on 2001 and was discovered by two eEye Digital Security employees. Melissa. Sasser. Zeus. Conficker. Stuxnet. Mydoom.
- In computing, a Trojan horse, or Trojan, is any malicious computer program which misleads users of its true intent. It is most dangerous computer virus.
Computer Threats:
- Advanced persistent threat
- Computer crime
- Vulnerabilities
- Eavesdropping
- Trojans
- Viruses
- Worms
- Malware
- Spyware
- Ransomware
- Rootkits
- Bootkits
- Keyloggers
- Screen scrapers
- Exploits
- Backdoors
- Logic bombs
- Payloads
- Denial of service
- Web application security
- Phishing
Safety/Defenses:
Computer access control
Application security
- Antivirus software
- Secure coding
- Secure by default
- Secure by design
- Secure operating systems
- Multi-factor authentication
- Data-centric security
- Firewall
- Encryption
- Intrusion detection system
- Mobile secure gateway
- Runtime application self-protection (RASP)
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Also see:
- Learn how to write the C program step-by-step | Lesson -1
- Learn how to write the C program step-by-step | Lesson -2
- Learn how to write the C program step-by-step | Lesson -3
- Learn how to write the C program step-by-step | Lesson -4
- Learn how to write the C program step-by-step | Lesson -5
- Learn how to write the C program step-by-step | Lesson -6
- Learn how to write the C program step-by-step | Lesson -7
Thanks a lot for reading.
What is Computer Viruses
Reviewed by Neel Kamal
on
February 11, 2019
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Reviewed by Neel Kamal
on
February 11, 2019
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