What is a virus - computer :: Computer Science

What is a virus - calculating machineWhat is a computer virusVirus ( data processor), self-duplicating computer programme that interfereswith a computers hardw atomic number 18 or in operation(p) system (the basic softwarethat runs the computer). Viruses are designed to iterate 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 book of instructions. These instructions are called the payload ofthe virus. The payload whitethorn disrupt or channelize data files, display anirrelevant or unwanted message, or subject 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 mingled heart and tries to vitiate the computers files orthe operating system. For example, it may copy part of itself to disket te disks, to the computers hard drive, into legitimate computerprograms, or it may conquer itself to e-mail messages and spread acrosscomputer networks by infecting other divided up drives. Infection is muchmore frequent in PCs than in passe-partout mainframe systems becauseprograms on PCs are exchanged primarily by means of floppy disks,e-mail, or over unregulated computer networks.Viruses operate, replicate, and deliver their payloads all when theyare run. Therefore, if a computer is simply attached to an infectedcomputer network or downloading an infected program, it will notnecessarily fetch infected. Typically a computer user is not likelyto knowingly run potentially harmful computer code. However, virusesoften trick the computers operating system or the computer user intorunning the viral program. nigh viruses have the ability to attach themselves to otherwiselegitimate programs. This attachment may occur when the legitimateprogram is created, opened, or modified. When th at program is run, sois the virus. Viruses potentiometer also 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 felled seam in the software that allows theuser to log on (gain access to)Types of VIRUSThere are five 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 identified 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 each direct-action orresident. A direct-action virus selects one or more programs to infect