Every computer needs to secure the data form virus unauthorized users and attackers. There are many types of security software including antivirus software, encryption software, firewall software and spyware removal software.  Computer security is also known as cyber security or IT security. It is the protection of computer systems.

Methods to Provide Protection There are four methods of protection.
1. System Access Control: It doesn't allow unauthorized users into the system and support the authorized users to protect the system. It inspires the users to change passwords frequently.
2. Data Access control: It observes who can get the information and for which purpose data can be used. Based on the security levels of the users, access rules can be determined by the system.
3. System and security Administration: Offline methodology is used to make or break the protected system. System and security administration can perform offline procedures.
4. System Design: The hardware and software security characteristics are used for system design.
Components of Computer Security

• Confidentiality: In this, the system cannot be accessed by unauthorized users


• Integrity: This term certifies that the information cannot be changed by unauthorized users.


• Access control: In this, users can get only permitted resources.


• Availability: It ensures that unauthorized user cannot access the system and make sure only authorized can access it.


• Cryptography: It is a process of protecting the information by storing on disk. It is an art of writing data in hidden or secrete format.


• The plain text can be converted into cipher text by using an algorithm, this process is known as encryption.


• Converting cipher text into plain text is called as decryption.

Types of Virus Virus stands for Vital information resource under siege. It is a software program that affects the system to corrupt the files in the form of executable files. The first computer virus is creepers and is developed in 1986.

• The virus is used for destruction purpose. It can copy itself and gets attached by itself to other files.


• The virus can attack over a network such as the Internet or removable disk like floppy disk, DVD, CD, and Pen drive.


• Virus can infect the computer and spread the infection. Computer virus includes all types of malware, and adware programs.


• Resident Virus: It is a type of virus that affects the system at run time. Usually, this type of virus is stored permanently in the computer memory and gets active to infect the files even after the harmful code is executed. E.g. Randex, and Meve.


• Direct Action Virus: If the file that consist the virus is executed, then this type of virus comes into action. This virus infects the files that are mentioned in the AUTOEXEC.BAT file path. E.g: Vienna virus


• Overwrite Virus: It is a type of virus that deletes the original file and replaces it with the new harmful file. Once it has been infected, it is not possible to clean the file. E.g. Way, Trj.Reboor, and Trivial.88-D.


• Boot Sector Virus: It is also called as a Master Boot sector virus or Master Boot Record Virus. It mainly infects the boot sector of a hard disk. E.g: Poly boot.B, and Anti EXE.


• Macros Virus: This type of virus affects the files that are created by using certain applications and contains macros. E.g: Melissa.A.


• File System Virus: Also known as Cluster Virus or Directory Virus, it affects the directory of the system and changes the path that is the location of a file. E.g. Dir-2 virus, etc.


• Polymorphic Virus: This type of virus affects system every time and encodes itself. This virus is used to make a large number of copies. E.g. Elkern, and Tuareg.


• FAT Virus: Usually, it stores the information about the location of files.  E.g. Link virus.


• Multipartite Virus: This virus can affect and expand in multiple ways.   E.g: Flip.


• Web Scripting Virus: This type of virus will occur in many websites at the time of execution code. This virus affects the computer via websites and these websites are created by infected code. E.g. J.S.Fortnight.

Effects of Virus

• Computer performance becomes slow and the speed of the computer will decrease.


• Data will be destroyed on local disks.


• The size of the memory will be increased or decreased.


• The computer network will be affected.


• Usually displays the error messages.


• Virus make disc as unreadable and creates empty files.


• Attacks: An Attack is an executed threat of computer system. The main source of attacks is the Internet. It mainly occurs from downloadable files. If any executable file like games is downloaded from internet, then it is essential to scan every file before downloading.


• Malware: A threat becomes an attack when it gets executed. Malware stands for Malicious Software and a number of malicious programs are used to damage the computer. Malware is a software that can run from anywhere by any unauthorized user.


• Worms: A computer worm is a malware program that can duplicate itself to spread to other systems. It sends replicated copies to other computers via computer networks. Worms are invisible files and are difficult to detect. E.g: Bagle, Morris, and Nimba.


• Trojan: A Trojan of Trojan Horse is a non-self-replicating type of malware. This term is obtained from the Trojan horse story in Greek methodology. The Trojan may injure host computer systems and can hack the computer system by unauthorized user.


• Antivirus Software: Antivirus software is application software designed to search, detect and remove viruses. It is a group program that can identify threats and removes computer viruses and malware. Spyware application is a small program embedded inside of a GIF image. Some popular Antivirus are Avast, k7, Tread Micro, Symantec McAfree AVG Kaspersky, Quick heal, and Norton.


• Firewall: A firewall can be hardware or software based program that helps in network security. A Firewall is used to control the network traffic and acts as a bridge between internal network and external network. It works with a proxy server.