A Cracker is similar to a hacker is the sense that he tries to gain unauthorized access to computer systems. However a cracker usually use this for malicious purposes and use persistence and the dogged repetition of a handful of fairly well-known tricks that exploit common weaknesses in the security of target systems. Crackers therefore are not known for their brilliance unlike hackers. Crackers are known for using off the shelf security programs rather than developing their own security software applications.