Passwords are still the most commonly used mechanism for user authentication. This paper proposes an efficient and effective method to attack passwords generated from some special keyboard patterns. The authors create a framework to formally describe the commonly used keyboard patterns of adjacent keys and parallel keys, called AP patterns, to generate password databases. Their simulation results show that the password space generated using AP patterns is about 244: 47 times smaller than that generated for a brute-force attack. They also design a hybrid pass-word cracking system consisting of different attacking methods to verify the effectiveness. Their results show that the number of passwords cracked increases up to 114% on average than without applying AP patterns.