A common threat web developers face is a password-guessing attack known as a brute force attack. A brute-force attack is an attempt to discover a password by systematically trying every possible combination of letters, numbers, and symbols until you discover the one correct combination that works. If your web site requires user authentication, you are a good target for a brute-force attack.
An attacker can always discover a password through a brute-force attack, but the downside is that it could take years to find it. Depending on the password’s length and complexity, there could be trillions of possible combinations.