What is a Hacker?

Hacker is a term used to describe different types of computer experts,
who employ a tactical, rather than strategic, approach to computer
programming, administration, or security. An exception to the expert
sense is use of the term by the popular media and the general
population to mean “computer criminal,” with no indication of level of
skill, expertise, or understanding implied. In the field of computer
security, hacker translates to a person able to exploit a system or
gain unauthorized access through clever tactics and detailed knowledge.
In computer programming, hacker means a programmer who hacks or reaches
a goal by employing a series of small changes or additions to exploit
or extend existing code or resources. In technical fields outside of
computing, hacker is sometimes extended to mean an expert who has
particularly detailed knowledge or cleverly circumvents limits.” – http://en.wikipedia.org/wiki/Hacker