An ethical hacker tries to attack a system like a criminal would attack a system, but the ethical hacker is authorized to evaluate the security of the system and will report his or her findings to the organization so vulnerabilities can be remediated rather than exploited. When considering how to learn ethical hacking, the skills needed will depend on the system or the application under evaluation, but typically require complex technical knowledge of the inner workings of protocols or systems to be able to identify exploitable vulnerabilities.
An unethical hacker, or black hat, will attack a system for his or her personal gain and exploit vulnerabilities to steal sensitive data, install malicious software or other actions, generally with the purpose of making money. Black hats may identify new vulnerabilities in the course of their work, but do not share the details of the vulnerability with the organization under attack or the party responsible for the software; they exploit the vulnerability for their own illicit gain, or sell the knowledge so others can.
The idea of an ethical hacking career has significantly risen in popularity over the last couple years, in part because of the high-profile status in the security community of people who find significant security vulnerabilities, along with the PCI DSS requirement for penetration testing, a form of ethical hacking.
This was first published in August 2010