Aircrack is a suite of tools for 802.11a/b/g WEP and WPA cracking. It implements the best known cracking algorithms to recover wireless keys once enough encrypted packets have been gathered. . The suite comprises over a dozen discrete tools, including airodump (an 802.11 packet capture program), aireplay (an 802.11 packet injection program), aircrack (static WEP and WPA-PSK cracking), and airdecap (decrypts WEP/WPA capture files).
For downloads and more information,
visit the Aircrack homepage.
I used Aircrack last year to gain access on a WEP secured connection. I enjoyed the reliability of the program and how simply it worked. It took about 20 minutes or less, very useful, speed depends on the network activity
Wonderfully fast WEP cracker. Longest time it's ever taken me to crack a WEP with this is about 10 minutes. Fastest time with this tool was like 20 seconds. Cracking WPA is still a joke, expect months to years, even with the highest end of computers. Don't bother using is on windows though, it is made specifically for linux. You can buy a certain USB Wireless module that aircrack will work with for like 25 bucks, but not sure how well it works.