The Virus:
A virus can be defined as a malicious program, that breaks into the computer without the consent of the user and sometimes even without the knowledge of the user. Viruses are also of different types and categories.
There are certain kinds of malware and spyware that enter a computer and start encrypting the user's data. Generally, a user gets to know about the existence of a virus when the computer programs begin to misbehave. Some files get corrupted and the user can't access them anymore.
Some files and programs may also get deleted as if they weren't even present on the system. But in case someone has installed good anti-virus software, they will get a notification as soon as some file containing some kind of virus enters the computer.
