Hacking can do great service or great harm. The white hats are true hackers, and consider themselves part of a noble profession. By discovering and reporting vulnerabilities, hacker groups worldwide play a valuable role in the advancement of security technologies and products. The Cisco Secure Consulting Services team, for example, is a team of white-hat hackers whose mission is to discover vulnerabilities in their clients' networks and recommend ways to secure them. Their activities are invited and legal.
True hackers refer to their black-hat counterparts as crackers, vandals, or intruders.
Crackers perpetrate crimes for political gain, economic advantage, social status, or simple amusement. They are by nature unpredictable, often malicious, and certainly unwelcome. They deface Web pages, crash computer systems, steal or damage confidential information, and disrupt business. These are amateurs who find hacking tools on line and use them without understanding how they work or what damage they can do. The external perimeter is a known risk, and most people have some kind of defense in place.