This article shares Penetration Testing techniques and tools for Wi-Fi networks to assess security controls for the router and wireless protocols being used.

http://www.pcmag.com/article2/0,2817,2477437,00.asp

How to Hack Wi-Fi PasswordsYour intensions when cracking a Wi-Fi password are no doubt noble—we trust you—so here’s how to do it    Once you’re asked for a username/password, what do you do? Check your manual. Which you probably lost or threw away. So instead, go to RouterPasswords.com. The site exists for one reason: to tell people the default username/password on just about every router ever created.

Or, create a system just for this kind of thing, maybe dual-boot into a separate operating system that can do what’s called “penetration testing”—a form of offensive approach security, where you examine a network for any and all possible paths of breach.  Kali Linux is a Linux distribution built for just that purpose. You can run Kali Linux off a CD or USB key without even installing it to the hard drive.

Aircrack has been around for years.  It goes back to when Wi-Fi security was only based on WEP (Wired Equivalent Privacy).  WEP was weak even back in the day, and was supplanted in 2004 by WPA (Wi-Fi Protected Access).  The latest Aircrack-ng 1.2—labeled as a “set of tools for auditing wireless networks,” so it should be part of any network admin’s toolkit—will take on cracking WEP and WPA-PSK keys.

Cracking stronger WPA/WPA2 passwords and passphrases is the real trick these days. Reaver is the one tool that looks to be up to the task (and it’s part of the BackTrack Linux distro). You’ll need that command-line comfort again to work with it, or you’ll have to spend $65 for Reaver Pro, a hardware device that works with Windows and Mac. After two to 10 hours of trying brute force attacks, Reaver should be able to reveal a password… but it’s only going to work if the router you’re going after has both a strong signal and WPS (Wi-Fi Protected Setup) turned on.