In ethical hacking and penetration testing, a dictionary used for brute-force or dictionary attacks is afile containing a list of potential passwordsthat an attacker or tester attempts against a target authentication mechanism. Therefore, option C is the correct answer.

Dictionary files are typically plain text documents that include commonly used passwords, leaked credentials, default passwords, variations of words, and patterns frequently chosen by users. Ethical hackers use these dictionaries duringpassword auditing and authentication testingto assess the strength of password policies implemented by an organization.

Option A is incorrect because a traditional language dictionary explains word meanings and is not structured for authentication testing. Option B is also incorrect because passwords are not normally stored in readable plain text documents; secure systems store passwords using hashing and salting mechanisms.

From a security perspective, dictionary attacks exploithuman behavior, particularly the tendency to choose weak or predictable passwords. Ethical hackers simulate these attacks in controlled environments to demonstrate the risks of poor password hygiene. The results help organizations enforce stronger password policies, multi-factor authentication, and account lockout mechanisms.

Understanding dictionary-based brute-force attacks is essential for managing attack vectors, as credential compromise remains one of the most common entry points for attackers. Ethical use of dictionaries allows organizations to proactively identify weaknesses before malicious actors exploit them.