White Hat Hackers
These are the ones who are termed as ethical hackers. These are the ones who follow morality, ethics, abide by the laws and still hack! It seems weird, but yes, that's how it is! An ethical hacker is permitted to hack computer systems or networks. Now the question arises - why?
An obvious answer to this is that unless there is an understanding of what is insecure in our system or network, we won't be able to protect it. An ethical hacker provides with vulnerabilities in the system or network, through use of various hacking techniques. These vulnerabilities are then generally corrected through corrective and preventive measures.
Black Hat Hackers
Black hat hackers, also called Crackers, are people who break into computer systems and networks without any prior permission. They are the people who hack for various reasons such as robbery, revenge, showing-off their skills, causing damage, or just any random reason. These people are regarded as the new criminals of this digital age.
Several federal laws have been enacted to curb black hat hacking. The IT Act 2000, which is followed in a number of countries, has listed out several ways to deal and punish these criminals.
A lot of network security agencies have been formed after many hacking cases were reported. These agencies work in designing security policies and measures to protect organizations and individuals alike, from getting hacked.
Grey Hat Hackers
They have their own reasons to hack computer systems and networks. They are like Robin Hood(s) of today's age. They can be seen as a mix of white hat and black hat hackers. Grey hat hackers can do good for some people and can even cause damage, depending on their approach.
For example, they typically hack sites which they feel are socially bad, like adult and gambling sites. Some, hack systems and networks to find out the vulnerabilities and loop holes, and report them to the respective organizations or owners. They do this for gaining popularity or some reasons and visions, best known to them.