Antivirus utilities are often used to cure a computer

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Unformatted text preview: a. A backup utility is used to create copy of data on some storage media such as floppy disk, CD-ROM, or magnetic tape that can be stored off-line away from the computer system. When some data stored on-line gets damaged or lost, it can be restored from the backup media. It is not necessary that the backup media is always kept off-line. In today's era of computer networks, some backup devices are kept online at a place away from the main computer system and the data backup is done automatically by the computer system on this device. Antivirus Utility A computer virus is a piece of code attached to a legitimate program that, when executed, infects other programs in the system by replicating and attaching itself to them. In addition to this replicating effect, a virus normally does some other damage to the system, such as corrupting/erasing files. Therefore, due to its spreading nature, a virus can cause severe damage to a system. A typical virus works as follows. The intruder writes a new program that performs some interesting or useful function (such as some game or utility) and attaches the virus to it in such a way that when the program is executed the viral code also gets executed. The intruder now sends this infected program by mail to other users of the system or offers it for free or for a nominal charge on floppy disks. Now if anyone uses the infected program, its viral code gets executed. When the viral code of the infected program executes, it randomly selects an executable file on the hard disk and checks to see if it is already infected. Most viruses include a string of characters that acts as a marker showing that the program has been infected. If the selected file is already infected, the virus selects another executable file. When an uninfected program is found, the virus infects it by attaching a copy of itself to the end of that program and replacing the first instruction of the program with a jump to the viral code. When the viral code is finished executing, it executes the instruction that had previously been first and then jumps to the second instruction so that the program...
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