Brute force attack
What is a Brute force attack?
In a brute force attack, the attacker attempts to bypass a security check by attempting possible options until finding one that works. The attacker attempts to exhaust the search space as efficiently as possible. With knowledge of the size of the search space and the rate that attempts can be made, one can calculate the length of time the brute force attack is likely to take.
Common uses of the attack technique
Brute force attacks are frequently used to attempt bypass of password based authentication schemes and cryptographic protection.
This kind of attack can also be used in attempt to discover web directory structure, ans is then said to be a URL brute force attack.
DIRB from http://sourceforge.net/projects/dirb/