A virus in computing word is a program developed by people. Virus programs are developed to cause issues for users. Virus usually try to lock or delete files on a computer. Viruses are programmed to scan the whole hard disks and make copies of them self to spread all around your computer.
A virus can be downloaded from Internet or copied over form an external disk such as a USB drive. Windows OS does not come with any virus when its fresh. A virus may not need your permission to be installed on your computer.
Most Viruses can be detected and removed by an Antivirus but sometimes it is too late or not possible to deal with a virus and you are left with no choice but formatting the hard disk. A computer virus can not harm the hardware on your PC directly. How ever if they make your CPU and Ram engaged by running multiple tasks, then your hardware may face issues for running up to their max power.
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