A person who uses his or her computer expertise to gain unauthorised access to other people's computers in order to obtain information illegally or cause damage is called what?

Introduction / Context:
This question belongs to the field of cyber security and computer ethics. Many terms are used to describe people who interact with computer systems in different ways. One of the most common exam questions is about the term used for individuals who break into computer systems without permission. Knowing the correct term helps learners understand news reports about security incidents and study basic concepts of information security and cyber law.

Given Data / Assumptions:

• The question describes someone who uses computer expertise to gain access to other computers without authorisation.
• This person may obtain information illegally or cause damage to systems.
• Options include spammer, hacker, instant messenger, programmer and technician.
• We assume the question uses the common meaning of the word used in exams and general discussion.

Concept / Approach:
In popular and exam oriented computer terminology, a hacker is someone who uses advanced computer skills to gain unauthorised access to systems, networks or data. Such access is often illegal and can be used to steal information, modify data or disrupt services. Although some communities use hacker in a more neutral or positive sense, question writers typically use it to mean malicious intruder. A spammer is someone who sends large quantities of unwanted emails or messages. Programmers and technicians may have deep technical knowledge but do not necessarily misuse it. Instant messenger is a communication tool, not a person. Therefore, hacker is the correct term for the person described in the question.

Step-by-Step Solution:

Verification / Alternative check:
Cyber security awareness campaigns, news articles and exam preparation guides frequently use the term hacker when discussing breaches where individuals break into systems. They talk about hackers stealing data, defacing websites or deploying malware. They also refer to ethical hackers who test systems legally, but the core idea remains that a hacker is someone skilled in gaining access. In contrast, spammer is used only in relation to sending unsolicited messages. This consistent usage across many contexts confirms that hacker is the correct answer for the described behaviour.

Why Other Options Are Wrong:

• Spammer: Sends large volumes of unwanted messages but does not necessarily break into computer systems.
• Instant messenger: This is a software tool or service for communication, not a person.
• Programmer: Writes code and develops software but is not automatically associated with illegal access.
• Technician: Installs, maintains or repairs equipment; again, the role does not imply unauthorised access or damage.

Common Pitfalls:
Some learners may confuse spammer and hacker because both are involved in cyber issues. However, the key difference is that spammers send unsolicited messages while hackers actively break into systems. Exam questions that mention gaining access, illegally, damage or stealing data are usually referring to hackers. To avoid confusion, remember that spam is about unwanted communication, while hacking is about unauthorised access to systems and data.

Final Answer:
A person who uses expertise to gain unauthorised access and cause damage is called a Hacker.