Networking

Welcome to the future: cloud-based WPA cracking is here

A security researcher has brought us in touch with the future of distributed computing: network encryption cracking. Chad Perrin explains how it works.

A security researcher has brought us in touch with the future of distributed computing: network encryption cracking.


In 2008, I speculated about the future of distributed security cracking. That future has arrived, in the form of a $17 "cloud" based service provided through the efforts of a security researcher known as Moxie Marlinspike. It is effective against pre-shared key deployments of both WPA and WPA2 wireless networks.

The mechanism used involves captured network traffic, which is uploaded to the WPA Cracker service and subjected to an intensive brute force cracking effort. As advertised on the site, what would be a five-day task on a dual-core PC is reduced to a job of about twenty minutes on average. For the more "premium" price of $35, you can get the job done in about half the time. Because it is a dictionary attack using a predefined 135-million-word list, there is no guarantee that you will crack the WPA key, but such an extensive dictionary attack should be sufficient for any but the most specialized penetration testing purposes.

If you opt to use the service, you will of course leave a money trail via Amazon Payments — which is probably a bad idea if you are attempting to gain unauthorized access to a secured network illegally. For the good guys testing the security of a client's network, however, this is an incredibly handy tool to have at one's disposal.

It gets even better. If you try the standard 135-million-word dictionary and do not crack the WPA encryption on your target network, there is an extended dictionary that contains an additional 284 million words. In short, serious brute force wireless network encryption cracking has become a retail commodity.

Some might question whether rainbow tables serve the purpose of penetration testing more effectively. In some cases they might, but rainbow tables face some limitations. From the FAQ for WPA Cracker:

Aren't there rainbow tables now?

Yes, the Church Of Wifi has put a large rainbow table collection online. However, there are a few ways in which this collection has not met our needs. The first is that since each handshake is salted with the ESSID of the network, you have to build a unique set of rainbow tables for each network that you'd potentially like to audit. The Church Of Wifi has gone to heroic efforts to build tables for the 1000 most popular ESSIDs, but we find that this is often not enough. If someone has enabled WPA encryption on their wireless network, chances are that they've changed their ESSID to something that's not very common as well.

Additionally, since they had to build so many sets, they had to limit the size of their dictionary in order to keep the resulting tables manageable. We feel that 1,000,000 words is really not large enough to do a comprehensive search, and that the way the dictionary was constructed discounts some of the specifics for WPA network password requirements. WPA Cracker provides a service that can crack the PSK of a network with any ESSID, using a dictionary that is several orders of magnitude larger.

The FAQ also claims that WPA Cracker uses a dictionary specialized for WPA cracking purposes, making it better suited to this specific purpose than the OpenWall dictionaries, which are "tailored more specifically for Unix logins than for WPA networks."

The interface is simple and clean, and the service does not require any more information from its users than an email address to deliver the results, the network's ESSID, and a network traffic capture that includes the encrypted WPA handshake. Payment information is handled by Amazon. If you have despaired of a simple and quick way to perform a penetration test on a WPA encrypted network without spending entirely too much money, the answer appears to have arrived.

About

Chad Perrin is an IT consultant, developer, and freelance professional writer. He holds both Microsoft and CompTIA certifications and is a graduate of two IT industry trade schools.

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