computer virus

computer virus

A computer virus is a piece of software that attaches itself to another program to corrupt the program and files on the computer system.
Types of Computer Virus
Computer Viruses are classified according to their nature of infection and behavior. Different types of computer virus classification are given below.
1. Resident virus: They usually fix themselves inside the computer memory. They get activated every time the OS runs and end up infecting other opened files.They hide in RAM.Examples CMJ,Randex,Mrklunky etc.
 2. Overwrite Virus: These types of viruses delete any information in a file they infect, leaving them partially or completely useless once they are infected. Once in the computer, they replace all the file content but the file size doesn’t change.examples trivial.88.D,trj.Reboot etc
3. \Boot sector: A Boot Sector Virus infects the first sector of the hard drive, where the Master Boot Record (MBR) is stored. . If a computer is infected with Boot Sector Virus, when the computer is turned on, the virus launches immediately and is loaded into memory, enabling it to control the computer. examples poly boot,AntiEXE,stone virus,disk killer,form etc
4. Macro virus: Macro viruses infect files that are created using certaing applications e.g ms office suite, these macros are usually stored as part of the document or spreadsheet and can travel to other systems when these files are transferred to another computer.examples Relax,Bablas etc
5. Directory Virus: Also known as cluster virus or file system virus. They infect the computer’s directory by changing the path indicating file location. They are usually located in the disk but affect the entire directory. Example is any file with the extension .EXE or .COM 3
6. \Polymorphic virus: Polymorphic Viruses have the capability to change their appearance and change their code every time they infect a different system.This helps the Polymorphic Viruses to hide from anti-virus software.examples are Elkern,Marburg,etc.
Effects of virus
It causes computer to crash (i.e. to stop functioning normally or to stop responding to other software) Loss of files and corruption of data stored in file.
Virus warning signs 
When a computer is infected with virus, the following symptoms may occur
 Slow system performance
 Presence of tiny dots
 Incomplete saving of files
 Appearance of strange characters
  Corruption of the system set up instructions
 Wandering across the screen
 New windows keep opening up at an alarming rate
 when files and folders getting deleted
  when disks and drives are not working properly
 Sources of Virus
  Infected storage devices such as flash drive ,CD-ROM etc
 By downloading or opening attachments in email from unknown source
 Through internet download
 Installation of infected programs
  opening an infected document
  by downloading cracked and illegal versions of software

MALWARE PROGRAMS
Malware is an abbreviated term meaning malicious software.it is a program that is specifically designed to gain access to or damage the computer files without the knowledge of the owner. It is developed for the purpose of doing harm to files, software and hardware.Computer Virus is one of the examples of malware.
 Other malware programs include;
Computer Worm: This is a program that uses computer network to spread itself.
 Trojan Horses: This is illegal instructions placed in the middle of a legitimate program.It is hidden program that runs on your computer without your knowledge.
Logic Bombs: This type of malware do not replicate, they are designed to destroy data on the computer system once certain conditions have been met.
Spyware: It is written to spy through a legal software.it changes computer’s configuration and personal information.

VIRUS DETECTION SOFTWARE (ANTI-VIRUS) This is a program written by the programmer to get rid of computer viruses. Some anti-virus are programmed to kill the virus and the effect done to the computer while others prevent the virus from entering the computer system. Anti-virus software is computer software used to prevent, detect and remove malicious software. Examples are; karpersky,E-scan,Avast,McAfee, etc