very low frequency tech postings - dect/gigasets.writeback
Sun, 18 Jan 2009the "hidden" gigaset menu and how to use it as a poor man's attacking tool
before I get into the above title, lets step back, and let me drop a few word about our very first practical attack against DECT.
impersonating a FP (basestation)
In the DECT standard a mutual authentication between PP (portable part, the "phone") and FP (fixed part, the basestation) is forseen, but it is optional. In all cases we have examined only the PP is authenticated by the FP, but not vice-versa. That means a FP can be sure what PP it is talking to, but a PP is left blind as to whether the basestation is really the one it once was shipped with.
The attack is possible due to two big fuckups:
Please, get that fixed!
In this scenario the attacker still has a lot of margin. As mentioned above, directional antennas can help, but the second idea is to jam the original basestation just by radio interference. So our idea in the early stages of the project was to first implement a DECT radio jammer with the com-on-air card. But at that timeframe the com-on-air card was still a big miracle to us, and really being able to use it only started at december 4th 2008. While the com-on-air jammer is technically possible we have never gotten down to implementing it, maybe one bored day we will...
Now back to the title and jamming with gigasets:
During the 25c3 BeF from the POC showed me a litte trick you can do whith almost all Siemens gigasets (or magenta clones):
this is fun so far, but doesn't jam yet. Now for jamming re-enter the service menu (keep 1 4 7 pressed while powering on, enter 76200), and select SAR from the menu. SAR means "specific absorption rate" and is a measure of the radio emission a device creates. When selecting SAR you will end up in another menu "1 slot"/"1slot low"/"2 slot" or the like... select the "biggest" one. The menu items probably heavily depends on what your phone supports of halfslot/fullslot/longslot/doubleslot/ecomode. Finally you're confronted with another selection fLOW/fCENTER/fHIGH. Select fLOW for jamming channel 0, fCENTER for jamming channel 5, and fHIGH for jamming channel 9.
here's my measurement setup using a spectrum analyzer with a crappy GSM antenna and a recent gigaset
The gigaset guys seem to have gotten the channel/frequency mapping wrong, their fLOW is the highest DECT frequency, their fHIGH is the lowest DECT frequency; DECT channels go from 0-9 starting at the highest frequency, and channel 9 being the lowest frequency. Here's what I measure with the gigaset jammer:
Now if our attacker is lucky she find's the victim's FP in channel 0, 5 or 9. She can also wait until it jumps there. She adds a directional antenna to her crappy old gigaset, pointing to the victim's PP, and is much more efficient with the above attack.
what the manufacturer of the spectrummazzoo wrote