Which of the following is a characteristic of a brute-force attack?

A brute-force attack is characterized by its method of attempting to gain unauthorized access by systematically guessing various combinations of passwords or encryption keys until the correct one is found. This approach does not rely on any prior knowledge of system architecture or specific vulnerabilities beyond the input mechanism for passwords. Each guess is made regardless of the application's specific configuration or security measures, which is why this method can be time-consuming and often requires considerable computational power, especially when strong, complex passwords are used.

In contrast, tactics such as social engineering are inherently different since they involve manipulating individuals into divulging confidential information rather than attacking the system's security through technical means. Similarly, SQL injection techniques target vulnerabilities in a database-driven application, leveraging the application’s interaction with the database rather than brute-forcing authentication credentials. While understanding the system architecture can enhance a hacker's approach to exploiting weaknesses, it is not a necessity for executing a brute-force attack, which solely depends on the password guessing process.