Types of Hackers

There are thee types of hackers white hat, grey hat, and black hat hackers. 

A White Hat (or, more properly, a "computer security specialist" or similar) will NEVER attempt to break into a system that they do not own or do not have explicit permission from the owner to do so. That means, they will usually be hired by a system or software owner to test the security of the said system or software package. They will always report their findings to the owner of the system, though there is somewhat of an ethical responsibility to report any significant (i.e. things that would impact the public) exploits to the community-at-large, if the original owner does not seem to be willing to address the issues - e.g. in case of a coverup of the problem, a White Hat is generally ethically bound to report the problem to the proper authorities, which may include public organizations such as CERT. More concisely, a White Hat is a professional, who abides by professional ethics and performs his or her duties out in the open. 

Grey Hat folks generally don't have obvious ill intent (to contradict the previous answer). That is, they're not looking to exploit any problems for personal gain. However, they generally follow an ethic which believes that it is OK to perform intrusion and exploit scans on systems which they DON'T own or have permission to do so. This makes it hard for a target to determine the difference between a Grey and Black Hat hacker, as the initial method of operation looks identical. That said, Grey Hat folks generally report their findings to the target - that is, they'll inform the target as to what security issues they have found. Most Grey Hats will give the target a small window to address the issues; however, a GH will always report the issue to the wider media and security groups, and will NOT consider any information that the target wants to keep private. That is, GH folks seem to see themselves as "defenders of the public good", and that by exposing weaknesses of systems, they will ultimately force folks to be more secure. This is a plausible, but not provably true, scenario. Grey Hat folks are hobbiests and enthusiasts, who generally don't get paid for their work, but pursue it for personal reasons. They generally keep their identities masked (or at least don't usually broadcast them), as much of their work is quasi-illegal. 

Black Hat folks, of course, are in it for the money (one way or the other). They're targets will never be informed of breaches, and in fact, most BH folks strive to keep their exploits secret from everyone, as it allows them to sneak in and steal information of value undetected. Black Hat folks are pure criminals.

Hackers can also be divided in to groups as follow

• Type A (rookie hacker): This type of hacker is interested in new technology and hacks that others are preforming. What distinguishes these hackers from others is that they simply don't have the amount of computer expertise to preform many/any hacks. Every hacker starts out as a Type A.
• Type B (beginner): Has the know-how to solve basic/intermediate computer problems and write basic programs. If you are a Type B hacker, you will make numerous mistakes, some minor, some fatal.
• Type C (intermediate hacker): Comfortable fiddling with hardware and software alike. Likes to build computers, root cell phones and tablets, and test all electronic devices to their limits. Most Type C, D, and E hackers have their own websites and networks.
• Type D (expert hacker): King of all other hackers. Can hack almost any piece of software or hardware in almost every way imaginable. Becoming a Type D hacker takes a lot of practice and dedication.
• Type E (Business hacker): Turns computer knowledge into cash. Type E hackers can do things for money such as rooting devices, selling custom operating systems and programs, and fixing computer problems. These people are most often also Type C or D hackers.
• Type F (illegal hacker): Called "crackers" by some, you do not want to be one of these.