A brute force attack is a method used by hackers to gain unauthorized access to accounts or systems by systematically trying every possible combination of passwords until the correct one is found. This approach relies on the sheer computing power of machines to automate the guessing process, making it a straightforward but time-consuming technique. To defend against brute force attacks, users can implement stronger passwords, enable account lockouts after several failed attempts, and use two-factor authentication. These measures make it significantly harder for attackers to succeed, even if they have access to powerful computing resources.