It’s a well-know fact that WPA-PSK networks are vulnerable to dictionary attacks, though one cannot but admit that running a respectable-sized dictionary over a WPA network handshake can take days or weeks.

A low-cost service for penetration testers that checks the security of wireless networks by running passwords against a 135-million-word dictionary has been recently unveiled. The so-called WPA Cracker is a cloud-based service that accesses a 400-CPU cluster. For $34, it can run a password against all 135 million entries in about 20 minutes. Want to pay less, do it for $17 and wait 40 minutes to see the results.

Another notable feature is the use of the dictionary that has been set up specifically for cracking Wi-Fi Protected Access passwords. While Windows, UNIX and other systems allow short passwords, WPA pass codes must contain a minimum of eight characters. Its entries use a variety of words, common phrases and "elite speak" that have been compiled with WPA networks in mind.

WPA Cracker is used by capturing a wireless network's handshake locally and then uploading it, along with the network name. The service then compares the PBKDF2, or Password-Based Key Derivation Function, against the dictionary. The approach makes sense, considering each handshake is salted using the network's ESSID, a technique that makes rainbow tables only so useful.

Everything seems to be perfect, but for the fact that there exists another alternative to crack WPA passwords which allows to reach the same speed. Just instead of installing a 400-CPU cluster, it’s possible to set 4 top Radeons or about two Teslas and try Elcomsoft Wireless Security Auditor.