Threat types
Like biologic viruses computer ones can also pose various threat level. Some of them are absolutely innocuous while the other viruses can erase all information stored on your hard disk.
If one divides all existing viruses as to the level of threat they pose there will be three virus types:
Innocuous virus
Such viruses don't pose direct threat for they just replicate themselves. Developers create such viruses to try their hand at developing a virus program, to assert themselves or just to play a joke. However, don't forget that no matter how innocuous a virus may seem nevertheless it remains a virus doing some harm:
- Viruses overload computer resources thus decreasing their performance;
- If such virus is detected on the site of a company this fact will cast a blur on its reputation.
Low-hazard virus
Such virus doesn't perform any destructive actions in the moment of activation but in annoys users with various visual and sound effects and messages. They are as harmful as innocuous viruses. Note, that these viruses have a plus. User's anti-virus software notifies that something is wrong in the system. In such a way viruses warn users about some more serious troubles.
Destructive virus
This virus destroys all data stored on your computer. As a virus can't remain unnoticed for hours it usually attacks and removes service areas. It takes the virus few seconds to do this but later a user will not be able to find at least any important information on the computer. One will need professional knowledge and special utilities to recover the disk.
Modern destructive viruses not only damage hard disk data but also manage to reach the CM0S memory chip and flash memory.
Such kind of viruses also infects BIOS. It is a mini-program managing computer devices and the operating system. Without BIOS one can't install the system or boot the computer. That's why if a destructive virus damages or destroys BIOS a user will not be able to restore it at home. For this reason modern mainboards have two BIOSes. If one system is damaged or destroyed a user can always use another one to boot the computer and then copy it to the damaged BIOS.