What constitutes a successful brute force attack?

A successful brute force attack is defined by the ability to successfully guess a password after a series of attempts, often utilizing automated tools to try various combinations rapidly. This method relies on the principle that with enough time and computing power, an attacker can eventually find the correct password to gain unauthorized access to an account or system.

In this context, successfully guessing a password signifies the attacker has effectively bypassed security measures designed to protect against unauthorized access. This approach is purely reliant on trial and error, and if it concludes with the attacker being able to log in, it represents a clear indication of a compromised system or account.

Other options describe different aspects of security breaches but do not specifically encapsulate the nature of a brute force attack. For instance, breaking into a system without detection focuses on stealth rather than the methodology of password guessing, gaining access to a firewall implies bypassing perimeter defenses rather than the user credential aspect, and using a single password for many accounts highlights poor password hygiene rather than the mechanics of the brute force attack itself.