Brute Force Attack

Brute force attack is a computer cracking technique in which the attacker uses an automated program to try every possible combination for a password.This password attack does not attempt to decrypt any information but continue to try different passwords again and again to gain a authentication/access.The amount of time it takes to complete these attacks is dependent on length of the password.Traditional brute force attacks attempt to guess username and password combinations for services like FTP, SSH, or other authenticated

Example
Let us assume the password length is 3. we have characters set (abcdefghijklmnopqrstuvwxyz0123456789)
Number of Permutation to first character :
Upper case letters(26 )+Lower Case Letters(26)+10 Numbers =62
Total permutation to find Password:
62*62*62=238328 ways.
Thus the automated brute force program need to try for an 238028 possible password. You can also calculate the time take to complete the brute force attack from "Last Bit"

Tools for Brute Force Attack
Here,I suggest some of the tools to crack an password using brute force technique
Cain and Abel
Aircrack
L0phtcrack
Brutus

Advantage

Disadvantage