Understanding Terms in Cybersecurity

The question asks for the specific term used to describe an individual who gains unauthorized access to computer systems and performs malicious actions, such as defacing websites for fraudulent reasons. Let's look at the options provided and understand what each term generally means in the context of computer security.

Analyzing the Options

• White hat: A white hat hacker is an ethical security expert. They find vulnerabilities in systems with permission from the owner, often to help improve security. They do not act maliciously or without authorization. This term does not fit the description in the question.
• Hacker: The term "hacker" is often used broadly. Traditionally, it referred to skilled programmers who explored and pushed the limits of computer systems. In popular media, it's often used interchangeably with malicious actors. However, in cybersecurity, it's often categorized further. A "hacker" could potentially fit the description, but there is a more specific term for malicious activity.
• Cracker: A cracker is an individual who attempts to gain unauthorized access to computer systems or networks with malicious intent. This intent often involves stealing information, causing damage, or engaging in fraudulent activities like defacing websites. This definition aligns closely with the description in the question.
• Stacker: The term "stacker" is not a recognized term in the field of computer security or hacking. It might refer to concepts in programming (like a stack data structure) or other unrelated fields. Therefore, it is not relevant to the question.

Comparing Hacker vs. Cracker

While "hacker" is a general term, "cracker" specifically denotes the malicious aspect described in the question. Crackers are the 'bad actors' who break into systems illegally and with harmful intentions, contrasting with ethical 'white hat' hackers who operate legally and for good.

The key elements in the question are "breaks into computer systems without authorization" and "deliberately defaces Web sites for fraudulent purpose." These actions clearly indicate malicious and illegal activity.

Conclusion

Based on the definitions, the term that best fits the description of an individual who breaks into systems without authorization and deliberately defaces websites for fraudulent purposes is "cracker".