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Wi-Fi Fingerprints -- the End of MAC Spoofing?
judgecorp writes, "Wireless devices can be identified by variations in their radio signaling, known as their 'transceiverprint,' according to research reported in Techworld. The Canadian researcher, Jeyanthi Hall, related the prints to MAC addresses and got a positive ID for devices connecting to a Wi-Fi network, claiming 95% success with no false positives. Once they work out how to do this without a dedicated signal analyzer and neural network processing, it's the end of MAC spoofing on wireless networks."
Cool hack, but who cares. With proper authentication (eg, WPA), you don't need to worry about MAC spoofing as the packets won't authenticate right to the access point.
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They were doing this during World War II, using the unique characteristics and variations of transmitters to "fingerprint" them. Similar things were done with the way radio operators send morse code to help detect spies that had been compromised.
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I think the whole point of this article is that will no longer be a valid method of protecting your identity since you might be identified by your "radio fingerprint" or "footprint" or wtfever.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Wi-Fi fingerprinting is nothing new and we have tried the various techniques at our university but it simply does not work because the number of false positives is way too high for it to be practical and to be deployed in an environment with many users. We had support from one of the developers of the technology and after looking at the data and the floods of user complaints he even admitted that Wi-Fi fingerprinting is not practical and we had to give up on it.
OK, but will the variation on the caps and resistors remain consistent over the life of the WiFi card? Will an allowance be made for ongoing variations in the signal? If so, will it be exploitable?
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I work for Big Cellphone Company. We tried the same scheme in the mid '90s when analog phone cloning was all the rage (remember when it used to cost $1.50/minute? Ahhhhh, the good old days). It works, kind of.
The problem is you're not trying to decide whether or not to retry a packet, or what the transmit power should be. You're trying to decide whether or not to provide service, so you really can't afford to be wrong. We were never really able to get an acceptable reliablility in the wild.
Believe me, we had a huge incentive to roll this out to our network. The marginal bandwidth costs from fraud didn't hurt much, but when someone made a call to, say, Saudi Arabia on a cloned phone we got stuck with all the fees on the other end. A single cloning ring could cost millions, so Big Cellphone Company was willing to break the bank to get this to work.
Eventually we rolled out digital service, so the project got shut down. Cloning fraud was one of the reasons we were willing to give you a free phone if you switched over to digital. Well, that and the long-term contract.
And each transmitter was hand-built, using rather rough tools.
All these things ensured that each signal had it's own quirks, in time, frequency, and temperature. Radio ops could often identify transmitters by thepaerticular yawps, swooshes, and zaps of the signal. ot to mention, identifing the morse code operator by his particular "fist", i.e. spacing and other personal quirks.
Then during WW2 our side started using spectrumanalyzers to categorize each model of German and Japanese radar. Here again each transmitter tended to have its own set of quirks.
Now, surprise, the same thing gets rediscovered. On some low level each wireless card has some (shuddrr) analog controlled oscillators, frequency dividers, duplexers, antennas, and amplifiers, each with it's own slight amplitude, frequency, and phase characteristics.
So nothing new here. Not by like, almost 100 years.
Why would you rely on such a silly system?
ian
Yup. Hams have been doing it for decades. (Well, most of us have just been talking about it - since actually doing it requires rather expensive gear and jammers troublesome enough to be worth the effort.) I can only imagine governments have been doing it for a lot longer than that.
But jumping from its use as forensic tool to something which could be used for authentication / spoofing detection on cheap networking gear is far from trivial. It's hard to imagine most wifi users paying to add the necessary gear to their access points. No matter how wonderful your pattern matching algorithm maybe, you still need a sensitive front end and a very fast sample rate to get the data in the first place. It's hard to imagine a scenario where the hardware needed to identify tiny perturbations on a signal wouldn't be a lot more expensive than the hardware needed to detect the signal itself.
Even as a forensic tool, the low cost of computer networking gear leaves an obvious out for savvy hackers: just load up on $5 wireless cards whenever you see them on sale, and throw each away after every successful use. It's a whole lot easier for most people to swap out networking hardware than to replace amateur radio transmitters. You could still use it to distinguish in real time between a particular legitimate user and an outsider, but that doesn't buy you very much unless it's cheap and robust enough to leave running at all times on every access point.