Now that we have seen the different types of the viruses, let us see how these viruses infect a system.
A virus comes to a system from another infected system, may be by copying a progrm from the infected system, or booting and infected floppy, or from opening any infected file over the network.
A virus comes to a system from another infected system, may be by copying a progrm from the infected system, or booting and infected floppy, or from opening any infected file over the network.
Once a virus infects a system it becomes memory resident, every time the infected part of the system is used.
For example, a virus that has infected MBR, DBR, or the system files, will become active every time the system is switched on or a virus that has infected a .COM or.EXE program will become active when that particular infected program is run.
After becoming active in the memory, virus starts to monitor different activities of the system, such as the disk read/write operation, keyboard operation, system clock etc.
The worm part of lthe virus starts to replicate the virus to new programs and disks. The bomb part of the virus waits for some specific event to make the bomb active and does the destruction for which it is programmed.
When you suspect a virus, press reset key or turn the machine off and then boot from a protected floppy disk or CD-ROM and clean virus using some good anti-virus software.
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