What is a virus
VIRUS: – A computer virus is program written with the malicious intention of causing harm to the programs, files and data stored on the computer. It differs from a normal program in the sense that it has the ability to replicate and execute itself without any instruction from the user to this effect. In many respects, computer viruses replicated the spread among the computers the same way as the biological virus affect the human beings. They can enter a computer system via a variety of media. Once inside the system files. It becomes active and makes copies of itself, as many times as the program to which it is attached, gets executed. The virus thus multimedia very fast, spreads to other files, occupies space In both primary and secondary memory, overwriting their contents. This robs the computer of its software and causes the system to crash. A virus can spread through a variety of media. It can be an infected floppy, a network connection or anything that is used for the transfer of data from one computer to another computer virus cause damage to the computer’s data and continue to multiply until detected and cured by an antivirus software. They are also of different types and tend to infect boot sector, data, system files, executable files, etc.
COMMON TYPES OF VIRUS: –
WORM: – Worm are the viruses that spread by using e-mail. They look in the e-mail address book of a user and send themselves to all the address stored therein to infect them as well.
Worm viruses are normally found on network than on stand-alone systems as they get a chance to quickly spread to a lot of computers, using network as a medium example are scalper sobbing and swen.
TROJEN: – Trojan is a virus that hides some destructive program in a useful appearing program. For example, a program that shows cracker on your screen or offers a drawing tool may delete some that shows of your files, working in the background by being active in the memory. Most of the current viruses contain both Trojan and worm so that useful looking program may delete important files and data as well as replicate and spread using network examples are backdoor, W32. Azak and Nuker.
BOMB: – It is a virus that becomes active when a specific event occurs and destroy or corrupts the document and program files on a computer. For example, Jerusalem-b waits for Friday the 13th and deletes the program files execute on that day Saturday 14, Tuesday 13th, etc. are the other example of this category of viruses.
MBR Infector: – Master boot record infector virus infects the master boot records of the hard disc. It contains very important information regarding boot files and is read everything when a computer boots from hard disc and thus the virus resident in the MBR is loaded by BIOS. DOS boot record infector virus spreads through infected floppy discs and hard discs. Whenever an infected floppy or hard disc is used to boot a system, the virus becomes active and starts spreading and infecting other computers. An example of MBR virus are quox Danish boot, PC store, etc.
PROGRAM FILE INFECTOR: – Another type of virus that does not infect MBR or DBR but attaches to some executable programs such .COM .exe SRC, .SAY, .OVL, DLL, etc. these type viruses turn the useful programs into viruses programs and when these infected programs are executed , the viruses become active in memory and starting spreading. So when these programs are used they becomes active in the computer’s memory and starts its destructive work.
STEALTH VIRUS: – This type of virus keeps on changing its program code so that it doesn’t get detected by a virus scanner, it befools the virus scanner by making it check the uninfected program and not the infected program, which is copied somewhere else beyond the antivirus software or virus scanner’s detection. Examples are Frodo, and brain.
MACRO VIRUS: – Infect data files such as MS WORD i.e., .doc file MS_EXEL, etc. they spread quickly when the infected files are shared through internet and network such as LAN and WAN, etc. Example are Melissa WM.concept. A, blood hound Babylonia, etc