Well it looks like what happened to WEP all those years ago is going to happen to GSM now. The methods have been known, the theory is established but the breaking point is when freely available tools are published that makes it possible for anyone to perform the attacks even without really understanding what is going on.
The recent news about WPA2 being cracked generated a lot of discussion, mostly highly technical – which means that you don’t have to worry too much about WPA2 being insecure as the attack isn’t really viable and relies on the ‘attacker’ already being authenticated with the network. There are easily ways to do the same thing with good old ARP spoofing.
Independent researchers have made good on a promise to release a comprehensive set of tools needed to eavesdrop on cell phone calls that use the world’s most widely deployed mobile technology.
“The whole topic of GSM hacking now enters the script-kiddie stage, similar to Wi-Fi hacking a couple years ago, where people started cracking the neighbor’s Wi-Fi,” said Karsten Nohl, a cryptographer with the Security Research Labs in Berlin who helped spearhead the project. “Just as with Wi-Fi, where they changed the encryption to WPA, hopefully that will happen with GSM, too.”
The suite of applications now includes Kraken, software being released at the Black Hat security conference on Thursday that can deduce the secret key encrypting SMS messages and voice conversations in as little as 30 seconds. It was developed by Frank A. Stevenson, the same Norwegian programmer who almost a decade ago developed software that cracked the CSS encryption scheme protecting DVDs.
It seems that with this suite of tools and the right hardware kit it’ll be a LOT easier to snoop on GSM transmissions. This includes cracking the secret key for SMS messages as well as being able to listen to voice streams.
The rainbow tables required for the crack are rather large at 1.7TB but it allows the attack to be pulled off in a mere 30 seconds. And thankfully they are being offered freely rather than on a paid for basis. They are planning to push out a torrent for the files, which as long as people keep seeding it, will work well.
It has been designed to work seamlessly with 1.7TB worth of rainbow tables that are used to crack A5/1, a decades-old encryption algorithm used to protect cell phone communications using GSM, which is used by about 80 percent of the world’s mobile operators. A small confederation of researchers announced last year they were setting out to create the voluminous index, which exploits known weaknesses in the encryption formula.
Distributing the rainbow tables has proved to be a challenge to the project participants. Stevenson said people in Oslo, where he’s located, are welcome to exchange a blank hard disk for one that contains the data. Eventually, the group expects to make the tables available as a BitTorrent.
The GSM Alliance, which represents almost 800 operators in 219 countries, pooh poohed the universal snooping plan by characterizing the attack as theoretical and saying encryption wasn’t the only protection preventing eavesdropping on real-time communications.
That’s where another tool, called AirProbe, comes in. An updated version of the program, also to be distributed Thursday, works with USRP radios to record digital signals as they pass from an operator’s base station to a GSM handset. Combined with refinements in the open-source GNU radio, it works by pulling down voluminous amounts of data in real time as it travels to the targeted cell phone and storing only those packets that are needed to snoop on a call.
In all honestly I’m not really familiar with GSM protocols, encryption or their weaknesses as it’s not an area I’ve ever ventured into, so if any of you have any input on the above claims I’d be interested to hear it. Has this attack been possible for a while? Is it really a risk, or just another mostly theoretical attack depending on many factors to pull it off?
Either way it’s a pretty interesting story and I’ll be seeing where it goes.
Source: The Register
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