Brute Force Attack
A Brute Force Attack is an attack in which every possible combination of letters, numbers, or words is tried in response to a shared secret authentication prompt.
Password prompts are the most common targets of brute force attacks, which can be frighteningly effective. Without throttling controls, a typical seven-character password can be brute forced in a matter of minutes, an eight-character password in a matter of hours.
Even with throttling controls in place, attackers can easily bypass them for high-value targets by using a distributed botnet that makes attempts on a reduced-frequency schedule over a longer period of time, a form of brute force attack that can in many ways be classified as an advanced persistent threat (APT).