Virus
A virus is a cute little software that has programmed to destroy your programs and softwares and hard drives and anything that is related to your computer.
Virus comes in different names like Trojan Horse, Worms, Phishing, etc…
Virus can cause different effects and defects to your computer. Most of the time, having a virus in your computer is a bad problem and that virus could cause various effects to your computer especially to your hard drives and programs.
There some viruses that can cause very VERY heavy damage to your computer such as BrO_AcT. This virus can stop most antivirus programs, unables you to access your regedit, msconfig, and task manager.
Other viruses can cause other effects i’ll tell you a couple of viruses now.