a is a hacker who criminally breaches the security of a computer or network.

Brief Explanations:

In cybersecurity terminology, hackers are often categorized by their intent and legality of their actions using "hat" colors. A "black hat" hacker is an individual who violates computer security for personal gain or with malicious intent, such as stealing data, spreading malware, or damaging systems. This distinguishes them from "white hat" hackers (ethical hackers who find vulnerabilities to fix them) and "grey hat" hackers (who may violate laws but without inherently malicious intent).

Answer:

black hat