Damage that Viruses Cause

The main aim of viruses is to make your computer system unstable and cause harm to the data.

These cause damage by viruses can be in many ways. Some of the way that viruses can damage your computer system listed here:

Viruses can destroy file allocation tables (FAT) and lead to the corruption of an entire file system, resulting in the need to fully reinstall and reload the system.
Viruses can create bad sectors on the disk, destroying parts of programs and files.
Viruses can decrease the space on hard disks by duplicating files.
Viruses can format specific tracks on the disks or format the entire disk.
Viruses can destroy specific executable files and alter the data in data files, causing a loss of integrity in the data.
Viruses can cause the system to hang so that it doesn't respond to any keyboard or mouse movements.