Which scenario describes a brute-force attack on a password?

A brute-force attack on a password is defined as a method where an attacker systematically attempts every possible combination of characters to gain unauthorized access to an account. By utilizing password-cracking software, the attacker automates this process, allowing them to input numerous potential passwords in a rapid sequence until the correct one is found. This method does not rely on guessing or exploiting social behaviors, but rather on the sheer computational power to test various combinations until success is achieved.

In contrast, the other scenarios do not qualify as brute-force attacks. Guessing a previously used password stems from knowledge of past user behavior rather than systematic testing. Automated phishing involves tricking users into divulging their credentials instead of directly attacking the password itself. Lastly, social engineering tactics manipulate individuals into providing confidential information without attempting to crack a password through automated means. Each of these methods lacks the direct computational approach characteristic of brute-force attacks.