Computer hacking is modifying computer hardware or software to accomplish a goal outside of the creator’s original purpose. People who engage in computer hacking activities are often called hackers.
Malicious attacks on computer networks are officially known as cracking, while hacking truly applies only to activities having good intentions. Most non-technical people fail to make this distinction, however. It is extremely common to see the term "hack" misused and be applied to cracks as well.
Hacker Classification:
White Hat Hacker (Ethical Hacker): They are paid and working for a Government Agency or Companies to deliberately Hack into their Computer Mainframe to find any potential Weak Points in a Computer's Mainframe, and then figure out how to fix them.
Black Hat Hacker: They are also known as a cracker. They are the type of hacker that has malicious intent whenever he goes about breaking into computer security systems with the use of technology such as a network, phone system, or computer and without authorization. His malevolent purposes can range from all sorts cyber crimes such as piracy, identity theft, credit card fraud, and so. He may or may not utilize questionable tactics such as deploying worms and malicious sites to meet his ends.
Grey Hat Hacker: They are a combination of a black hat and a white hat hacker. A grey hat hacker may surf the internet and hack into a computer system for the sole purpose of notifying the administrator that their system has a security defect, for example. Then they may offer to correct the defect for a fee.
Elite Hacker: Elite hacker is the name utilized by the community with the aim of identifying those individuals who are deemed to be as experts in their line of work. These people are actually on the “cutting edge” of both the computer and network industry (Example:Master of Deception).
Script Kiddie: This is a derogatory term for black hat hackers who use borrowed programs to attack networks and deface websites in an attempt to make names for themselves.