aircrack-ng

wireless WEP/WPA cracking utilities
aircrack-ng is an 802.11a/b/g WEP/WPA cracking program that can recover a
40-bit, 104-bit, 256-bit or 512-bit WEP key once enough encrypted packets have
been gathered. Also it can attack WPA1/2 networks with some advanced
methods or simply by brute force.
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It implements the standard FMS attack along with some optimizations,
thus making the attack much faster compared to other WEP cracking tools.
It can also fully use a multiprocessor system to its full power in order
to speed up the cracking process.
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aircrack-ng is a fork of aircrack, as that project has been stopped by
the upstream maintainer.