Another poor sysadmin

Oops, not quite yet. These wireless A/V devices are using the free band at 2.4 Ghz and in this place there is a festival of telecommunication airwaves. Unfortunately, there was a lot of noise and there was no way somenone could enjoy a movie in this quality. Especially when using the microwave oven.

WiFi standard for wireless LANs is divided to 14 channels. The "good" channels 1,6,11 and 14 are already used. There is a fair amount of signal in channels 1-5 from various wireless APs in the close vicinity. Channel 6 is used by my indoor router. And channel 11 is used by another indoor router that belongs to one of my neighbours. Channel 14 is not legal in my country.

The A/V transmitter has only four channels available that are propably an equal division of the range 2.40-2.48 Ghz. None of them seemed to be unaffected by all this wireless network traffic. Then, I had an idea. My neighbour's wlan was unecrypted with free access, and I knew his router had the default password for its' administration interface ;-) . So I connected to his/her network, accessed the administration interface and changed the channel used from 11 to 1. Well, I figured that if s/he had let MS Windows to control the WiFi pccard s/he wouldn't notice any change since channel resolution in this case is automatic.

After that, the receiver was working fine in the 4th channel and finally I could happily watch the 'Pirates of Silicon Valley'.

What the heck this has to do with aircracking? A couple of days later the reception was bad again. I checked by scanning for networks and found out that my neighbour was using channel 11 again, and this time with WEP encryption. I guess, me changing the channel of his router did cause a problem to him/her. S/He must of contact the technicall support of his/her DSL provider which then advised him to use WEP encrytpion just as a precaution.

First, I solved the problem of the A/V reception by changing my own router's channel from 6 to 1 and my A/V transmitter to the 3rd channel (somewhere between channel 6 and 11 for WLANs) and then experimenting by placing the A/V transmitter and receiver in various locations until the received picture was clear. I actually got a nice result with the only disadvantage that my A/V receiver is now hanging on the edge on top of my TV.

And then, I was curious to see how secure WEP is. It is known to have very poor encryption that is easily exploited.

apt-get install aircrack.

Aircrack is a set of tools for hacking wireless networks. To crack a WEP encrypted signal someone first has to gather enough packets (or ivs) from the encrypted network by using the airodump tool. Then, aircrack tool analyzes the packets and calculates the encryption key.

Yesterday I left my laptop in airodump mode all day. When I came back home in the evening, airodump had gathered enough packets to crack a 128bit WEP key. It took less than two seconds for aircrack to provide me with a five bytes long hexadecimal key. My neighbour, typicall lame user, didn't bothered to think of a 128bit key (needs 11 characters instead of 5). What a surprise, s/he didn't even changed the default password for administration interface of his/her router.

This time though, I didn't mess with his/her settings, this was only for educational purposes (Actually, it was too easy to be of any other educational gain than that WEP is completely useless). Maybe I have to find out who is this neighbour and then use some of Kevin's social engineering to pursuade him/her to change the channel because it interferes with my A/V signal.