Final answer:
A hacker is someone who illegally accesses a computer system to exploit legitimate user accounts, using methods like phishing and breaking into websites.
Step-by-step explanation:
A hacker is an individual who is not authorized to use the computer and who penetrates a system's access controls to exploit a legitimate user's account.
Hackers have various methods to infiltrate systems, including breaking into websites, creating malicious links, and phishing attacks where they trick individuals into divulging sensitive information.
The goal of these unauthorized users often ranges from theft of data to vandalism or just the challenge of bypassing security measures.
The term you are looking for is "hacker." In the context you provided, a hacker is an individual who is not authorized to use the computer and who penetrates a system's access controls to exploit a legitimate user's account.
It's important to note that the term "hacker" can have different connotations, and not all hackers engage in malicious activities. Some hackers use their skills for ethical purposes, such as identifying and fixing security vulnerabilities.