Security expert Thomas Roth has used Amazon's EC2 cloud computing service to break the Wi-Fi protected access (WPA) encryption method often used to store Wi-Fi passwords. Roth took advantage of Amazon's new graphics processing unit (GPU) clusters to crack his neighbour's network in 20 minutes, and now says an updated version of his software could do the job in 6.

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Roth says that GPUs are hundreds of times faster than standard quad-core central processing units (CPUs) when it comes to cracking SHA-1, and Amazon provides a cluster of these processors for $2.10 per hour, allowing Roth to break into a Wi-Fi network for a theoretical cost of just 21 cents per password