MAC filtering is pretty simple to crack. Basically- as you probably know- the MAC address is just a unique ID assigned to each network device (Be it wired or wireless). MAC filtering tells the AP to only allow certian wireless devices. However when signals go out from the AP, the MAC address info is sent in the clear. Basically its out there yelling "HEY, I've got a web page here for 123abc, who is 123abc? anyone? anyone?" All someone has to do is intercept that message, change their MAC to 123abc and they are on the AP.

WEP's weakness gets tricky, someone else can probably explain this better than I can. But basically there is a pre-shared key that is used to generate the cryptography. The AP sends its part of the key and a request for the response to any device trying to connect. Widely available software can even stimulate the AP into sending even more data which. After there is enough data sent cracking software can determine the master key from all the peices.

WPA uses the same cryptography, but it takes the key and hases it something like 1024 times then changes it fairly often. It also encapsulates the key itself where as WEP sends it in the clear. Basically with WPA, once the secure connection is established, the key changes faster than it can be cracked. WPA CAN be cracked, but it requires someone to capture a LOT of data and use a powerful computer to run a brute force crack against it. So if you WPA password is something like "We Love Paris" even though it seems strong b/c its a sentence, all the words are in the dictonary so its subject to such an attack.

What I do, and Steve Gibson has recomended the same thing on a podcast, is use a random 63bit password. I keep it stored on an encrypted network share and on a USB key (that I keep locked in my wine fridge - only so I'll remember where it is). www.grc.com/pass has the best algorthim that I know of. WHat I HAD used wa something I downloaded for OS X, but I think Gibson's is probably a tad stronger. When you use a 63bit password WPA is uncrackable- mathmatically speaking.

Of course I'm also a freak- I don't want guests on my LAN so I have a seperate wireless subnet with an open access point that only uses MAC filtering. I have some WiFi phones that don't support WPA. So even if its cracked (and I craked it myself several times just to learn) then people can only get out to the internet and are not on my network. I'm not thrilled with that solution at all currently... but it means my phones work and my LAN is safe. On my LAN I use WPA2 with the affore mentioned 63bit password. So far I've never needed to have anyone join my LAN WiFi so the USB key is still next to the Turley and Martinelli zinfendels...

-N