These are people who attempt to penetrate security systems on remote computers. This is the new sense of the term, whereas the old sense of the term simply referred to a person who was capable of creating hacks, or elegant, unusual, and unexpected uses of technology. A hacker is a person who breaks into computers and computer networks, either for profit or motivated by the challenge. The subculture that has evolved around hackers is often referred to as the computer underground but is now an open community. In the words of Brian Harvey, of UCL, Berkeley, “A ``computer hacker,'' then, is someone who lives and breathes computers, who knows all about computers, who can get a computer to do anything. Equally important, though, is the hacker's attitude. Computer programming must be a hobby, something done for fun, not out of a sense of duty or for the money. (It's okay to make money, but that can't be the reason for hacking.)”. There are specialties within computer hacking. An “algorithm hacker” knows all about the best algorithm for any problem. A “system hacker” knows about designing and maintaining operating systems. And a ``password hacker'' knows how to find out someone else's password.
The Hacker Ethic
Every profession or trade tends to have an ethical code which suggests that it is capable of self-regulation of its members. The code demonstrates the shared core values necessary for people to practice within the professional community. And it enables the public and the government to have some degree of trust for the profession. Hackers have their own ‘code of honour’- the ‘Hacker Ethic’. The original Hacker Ethic was sort of an impromptu, informal ethical code developed by the original hackers of MIT and Stanford (SAIL) in the 50s and 60s. These "hackers" were the first generation of programmers, employing time-sharing terminal access to 'dumb' mainframes, and they often confronted various sorts of bureaucratic interference that prevented them from exploring fully how technological systems worked. The ethic reflects their resistance to these obstacles, and their ideology of the libratory power of technology. The idea of a "hacker ethic" is perhaps best formulated in Steven Levy's 1984 book, Hackers: Heroes of the Computer Revolution. Levy came up with six tenets:
- Access to computers - and anything which might teach you something about the way the world works - should be unlimited and total. Always yield to the Hands-On imperative!
- All information should be free.
- Mistrust authority - promote decentralization.
- Hackers should be judged by their hacking, not bogus criteria such as age, race, or position.
- You can create art and beauty on a computer.
- Computers can change your life for the better.
PHRACK, recognized as the "official" hacker newsletter, expanded on this creed with a rationale that can be summarized in three principles ("Doctor Crash," 1986).  First, hackers reject the notion that "businesses" are the only groups entitled to access and use of modern technology.  Second, hacking is a major weapon in the fight against encroaching computer technology.  Finally, the high cost of equipment is beyond the means of most hackers, which results in the perception that hacking is the only recourse to spreading computer literacy to the masses
Although hackers freely acknowledge that their activities may be occasionally illegal, considerable emphasis is placed on limiting violations only to those required to obtain access and learn a system, and they display hostility toward those who transgress beyond these limits.
The question of hacker ethics was brought to the fore during the trial of US Judge Ronald C Kline in 2002-2005. Kline stood accused of downloading child pornography to his home and courthouse computers. The evidence against him hinged on the credibility of a Canadian hacker named Bradley Willman, who claimed to have stolen an electronic diary from his computer. Kline's defence attorneys attacked the hacker's credibility, saying that taking the judge's diary was illegal and suggesting that the hacker was working on behalf of law enforcement at the time. Defence attorneys also raised the possibility that the hacker could have doctored the diary and computer images that form the bedrock of federal prosecutors' case against Kline. Finally, after a long drawn out legal battle that lasted 4 years, Kline was put behind bars in 2006, with Willman judged to have been acting independently of any government agency.
The case of the United States vs Kline is just one of many instances of hackers helping to put criminals behind bars, and it stands as a shining example of how hacking can be used to make the world a better place.