What is a virus - computer :: Computer Science

What is a virus - computerWhat is a VIRUSVirus (computer), self-duplicating computer program that interfereswith a computers hardw atomic number 18 or operational system (the basic softwarethat runs the computer). Viruses are designed to duplicate orreplicate themselves and to avoid detection. Like any other computerprogram, a virus must be executed for it to function-that is, it mustbe located in the computers memory, and the computer must then followthe viruss instructions. These instructions are called the payload ofthe virus. The payload may disrupt or change data files, display anirrelevant or unwanted message, or cause the operating system tomalfunction.Computer viruses activate when the instructions-or executablecode-that run programs are opened. Once a virus is active, it mayreplicate by various means and tries to defile the computers files orthe operating system. For example, it may copy parts of itself tofloppy disks, to the computers hard drive, into legitimate compute rprograms, or it may attach itself to e-mail messages and spread crosswayscomputer networks by infecting other shared drives. Infection is much more(prenominal) frequent in PCs than in professional mainframe systems becauseprograms on PCs are transfer primarily by means of floppy disks,e-mail, or over unregulated computer networks.Viruses operate, replicate, and deliver their payloads only when theyare run. Therefore, if a computer is simply accustomed to an infectedcomputer network or downloading an infected program, it will notnecessarily become infected. Typically a computer user is not probableto knowingly run potentially harmful computer code. However, virusesoften trick the computers operating system or the computer user intorunning the viral program. whatsoever viruses have the ability to attach themselves to otherwiselegitimate programs. This attachment may occur when the legitimateprogram is created, opened, or modified. When that program is run, sois the virus. Viruses can in addition reside on portions of the hard disk orfloppy disk that load and run the operating system when the computeris started, and such viruses thereby are run automatically. Incomputer networks, some viruses hide in the software that allows theuser to log on (gain access to)Types of VIRUSThere are volt categories of viruses parasitic or file viruses,bootstrap sector, multi-partite, macro, and script viruses.Parasitic or file viruses infect executable files or programs in thecomputer. These files are often set by the extension .exe inthe name of the computer file. File viruses leave the contents of thehost program unchanged but attach to the host in such a way that thevirus code is run first. These viruses can be either direct-action orresident. A direct-action virus selects one or more programs to infect