Interview on Security Weekly

I had a great time talking with Paul and company on the Episode 376 of the Security Weekly Podcast. We talked a little about HackRF, but most of the discussion was about Ubertooth and Bluetooth security. This conversation prompted me to write a full description of how we recover Bluetooth UAPs by passive monitoring with Ubertooth.

Appearance on The Amp Hour

In case further evidence is needed to demonstrate that I am a terrible blogger, I submit this: I had a wonderful time as a guest on Episode 161 of The Amp Hour and forgot to mention it here for nearly eight weeks! We discussed HackRF, Daisho, Ubertooth, wireless security, and how I came to the world of open source hardware from a background in information security. Thanks for having me on the show, Chris and Dave!

So You Want to Track People with Ubertooth. . .

Dominic started a blog for Project Ubertooth recently, so I will publish most future Ubertooth related content over there. My first post is a FAQ for people wanting to use Ubertooth to track the movements of Bluetooth devices.

Handing Over the Reins

Dominic Spill is now the lead developer of Project Ubertooth. I am so excited that he has agreed to take on the job!

A little over a year ago I packed hundreds of Ubertooth Ones into boxes and shipped them to my generous Kickstarter backers. Since then, I have worked to improve the Ubertooth software, but it has been hard to devote as much time to the project as I would like while simultaneously concentrating on other projects to keep Great Scott Gadgets going. A few months ago I realized I simply wouldn't be able to accomplish my goals unless I could get some help, so I started talking to Dominic about taking over. Thanks to everyone who has purchased Ubertooth One and the Throwing Star LAN Tap, we have finally made the arrangement a reality.

Dominic has been involved in Project Ubertooth since before it was Project Ubertooth. His work on gr-bluetooth and his paper with Andrea Bittau were the starting point for my early Bluetooth research, and Dominic and I made great strides together in a short period of time before presenting our results at ShmooCon 2009. As I started working on developing a low cost platform for Bluetooth monitoring, Dominic was there at every step along the way. His many behind-the-scenes contributions helped make Project Ubertooth what it is today.

Dominic's first task is to review a number of code contributions and modifications since the last software release and to make a new release. After that, he will focus on adding new features such as frequency hopping. Meanwhile he will be the primary person handling questions on the mailing list and coordinating contributions from other developers. I will continue to be involved (you can often catch us both on #ubertooth at chat.freenode.net), but Dominic is the lead developer going forward.

Thanks to everyone who has supported the project for helping us make this happen! We will do our best to make Project Ubertooth better than ever.

Bluetooth for Bad Guys

Criminals have been skimming debit and credit card information by tampering with point of sale terminals, PIN pads, gasoline pumps, and ATMs for quite a while now. The first time I heard of Bluetooth being used in such cases was from this SparkFun Electronics news blurb a couple years ago. Malicious hardware installed in a Canada retailer's PIN pad intercepted customer data and transmitted it via Bluetooth to the attacker's device, perhaps a laptop in a nearby parking lot. At the time it seemed like a clever use of the technology by a Canadian ne'er-do-well but probably not the start of a trend. I was wrong.

As Joshua Wright recently pointed out, Visa is informing merchants about similar crimes that took place around the same time in Utah. Skimmers have also been found in Florida and elsewhere. Just this week, customers of Lucky Supermarkets in California found out that a similar attack was the reason their bank accounts were recently drained. This isn't just one clever crook; this is a criminal industry at work.

The technical reasons that Bluetooth is an attractive technology for this application are nicely outlined in Joshua's article, but we wouldn't see so many actual attacks were it not for commercial availability of Bluetooth skimmers sold on the criminal underground. There is an industry producing hardware for crime just as there is an industry producing software for crime.

How can you protect yourself as a customer? The best advice I can think of is to consider the liability of payment methods. There is a reason I like to carry some cash. There is also a reason I strongly prefer to use a credit card over a bank debit card. With a credit card (in the US, at least), the financial institutions and merchants bear most of the burden of liability. As long as I check for unauthorized transactions before paying my bill every month, I don't have much to worry about. Once, many years ago, someone emptied my checking account. I figured out what had happened and managed to convince my bank that the bank's own misguided security practice had allowed it to happen, but guess who bore the burden of a zero balance until that was resolved?

How can you protect yourself if you are a retailer or financial institution? This is a much more difficult problem. For starters, you should read Joshua Wright's article and the Visa bulletin. Josh has some nice things to say about my Project Ubertooth, but he also has some criticisms, mostly pointing out features yet to be developed. The first item on his wish list is frequency hopping, something I am working on now. He also points out the need to improve Bluetooth device fingerprinting, an area of research that has been advanced in recent years primarily by JP Dunning.

When I read about real life attacks on retailers and customers, sometimes I imagine how I could use technology to catch the crooks. Frankly, it would be hard, and it would be especially hard to deploy tools that would allow more investigators to do the same. Bad guys are using Bluetooth (and potentially other wireless technologies). We need Bluetooth tools for the good guys too.

I guess, if there is a lesson to be learned from all this, it is that hardware security matters. If an attacker can get in between a user and a system, the security of the system will fail in almost any case. Advocates of the Bring Your Pwn Device (BYOD) trend might want to pay attention. (That was an honest typo, but I decided to keep it!)

Discoverability is Not a Mitigating Factor

Four years after BlueSniff: Eve Meets Alice and Bluetooth by Dominic Spill and Andrea Bittau, people are still saying that Bluetooth vulnerabilities can be mitigated by turning off discoverability. If there is one thing that should have been learned from all of the Bluetooth security research done over the last few years, it is that a non-discoverable device is no safer than a discoverable one, but perhaps this message has been buried too deeply in technical presentations. Let me try to make this point clearer.

A discoverable Bluetooth device is one that is willing to respond to an inquiry, a single packet transmitted by any device looking for others. When you tell a device to "find new Bluetooth devices" it transmits a large number of inquiry packets and waits for responses. A discoverable device's inquiry response contains information including the device's address (BD_ADDR). This address can then be used by the inquirer to initiate a connection between the two devices.

Since most Bluetooth vulnerabilities can only be exploited once a connection is established, people used to recommend turning off discoverability. The reasoning was that, without a way to learn the target's address, an attacker would be unable to connect to the target and exploit any vulnerability. This idea that it is possible to keep a Bluetooth device address secret is completely wrong.

Turning off discoverability is like hiding the SSID of an 802.11 network. It prevents people from casually or accidentally connecting to your Bluetooth device. It might be worth doing for this reason alone, but I no longer recommend it as a security practice. Turning off discoverability does nothing to thwart skilled attackers. Worse, it creates a false sense of security and makes it harder for the good guys to notice that Bluetooth devices are in use.

A BD_ADDR is a 48 bit number (it's a MAC address) that is unique to a particular Bluetooth device. It consists of three sections, the 16 bit Non-Significant Address Part (NAP), the 8 bit Upper Address Part (UAP), and the 24 bit Lower Address Part (LAP). In order to connect to a target, an attacker needs only the UAP and LAP.

LAP sniffing is easy. Every Bluetooth packet contains the LAP in cleartext. Spill and Bittau showed how to sniff LAPs with a USRP for about $1000. Now it can be done with an Ubertooth One for about a tenth of that price. It can even be done using Travis Goodspeed's method for promiscuous sniffing with lower cost platforms. LAP sniffing has always been easy, but now the tools and methods are more well known.

The UAP is only slightly more difficult for an attacker to learn. Project Ubertooth and gr-bluetooth include software that implements automatic UAP determination based on passive observation of just a few packets. The function is integrated into the Ubertooth Kismet plugin. Even without this method, it isn't hard to figure out the 8 bit UAP. In Hacking Exposed Wireless, Second Edition, Joshua Wright showed how to determine the UAP with a simple brute force attack.

Turning off discoverable mode doesn't make your Bluetooth device any more secure. If your security model depends on secrecy of the BD_ADDR, you are doing it wrong.

And, by the way, frequency hopping doesn't help you either.

Ubertooth spectrum analyzer

I took a break from hardware and manufacturing concerns tonight and sat down to write some code. I probably should have worked on the USB bootloader, but instead I wrote a simple spectrum analysis function for the Ubertooth platform. Similar to other transceiver IC spectrum analyzers (like my IM-Me implementation), it tunes its receiver to one frequency at a time and records the received signal strength before hopping to the next frequency.

For now I'm just dumping a table of values to a file and plotting it with gnuplot. In the future perhaps a more sophisticated user interface could be built, maybe integrating with Mike Kershaw's Spectrum Tools or something like that. In this plot, you can see a busy 802.11g network on channel 1 (centered at 2412 MHz) and some Bluetooth traffic (a device performing an inquiry scan) throughout the band.

While testing this, I tried pushing the limits of the CC2400's tuning range for the first time. The device I tested functioned with its receiver tuned from 2268 to 2794 MHz. (The supported range is 2400 to 2483.) I didn't actually generate test signals to validate that it could see stuff throughout the entire range, but my guess is that it is usable across the whole tunable range but with degraded performance at the extremes.

The spectrum analysis code is available in the Ubertooth repository and will be included in the next release. Let me know if you do anything interesting with it. There are just a few days left to pick up one of the first batch of boards by making a pledge on Kickstarter.

Project Ubertooth: Building a Better Bluetooth Adapter

Video of my presentation, Project Ubertooth: Building a Better Bluetooth Adapter, at ShmooCon 2011 is now online. You can download the entire video in high quality from shmoocon.org or watch it in your web browser. In the presentation, I demonstrated Ubertooth One, the world's first open source, widely available, low cost Bluetooth test tool, and I described my two year design journey starting as an electronics novice. This was one of the most fun talks I've ever given, and I want to thank ShmooCon for making it happen and everyone who attended for participating. I'm making the slides available, but, as is typical of my presentation slides, they really don't stand alone.

Shortly before the presentation, I was interviewed by Hak5. The interview covered a lot of ground and included quite a bit of discussion beyond the content of the presentation.

At ShmooCon I announced the start of a pledge period on Kickstarter to fund an initial production run of Ubertooth One boards, and the pledge goal was met in just four days! There is still time remaining in the pledge period for anyone who would like a board. Thank you to everyone who has pledged support!

first Bluetooth Low Energy packets

A package arrived today containing my first Bluetooth Low Energy equipment. Bluetooth Low Energy is a new wireless technology within the Bluetooth specification suite. It provides capabilities similar to Basic Rate Bluetooth, which has been around for ten years, but consumes less power while doing so. Consumer Bluetooth Low Energy products likely won't hit the market for a few months, but engineering development tools have recently become available.

This kit from Texas instruments contains a two small CC2540 development boards, one in the form of a keyfob and the other in a USB dongle form factor. For now I'm not interested in developing firmware for the CC2540. Frankly I'm annoyed that TI has chosen not to document the internal radio properly. Despite its limitations, however, this kit provides a quick and easy way to generate Bluetooth Low Energy wireless packets over the air, and I'm using it (so far just the keyfob) to help me develop Low Energy sniffing capability on the Ubertooth platform.

It only took a few minutes to tweak the Ubertooth code such that it would demodulate Bluetooth Low Energy packets properly, but I don't have much in the way of automated packet detection or decoding. Using a fairly crude method, I've searched through the demodulated bits to find the advertising packets transmitted by the keyfob. These are packets transmitted on one of only three advertising channels in an effort to locate another device to communicate with.

One of the key differences between Basic Rate and Low Energy is that Low Energy devices are able to locate each other and initiate communications using this advertising method much faster than Basic Rate devices ever could. Basic Rate devices waste a lot of power keeping connections alive; Low Energy devices will just tear down connections entirely and go to sleep knowing that they can wake up and find each other again very quickly. One of the reasons the method is fast is that advertising is only done on three channels, and that makes it easier for a passive observer to capture the process.

I've also captured the packets using a USRP. Glancing at the waveform and spectrogram, it is difficult to distinguish this packet from Basic Rate Bluetooth. I haven't written any GNU Radio code to demodulate the raw waveform, but I am replaying the recorded file through the USRP as a simple way to produce a repeatable test vector.

Ubertooth One on Kickstarter

At ShmooCon over the weekend, I gave the first public demonstration of Ubertooth One, a smaller and more powerful Ubertooth hardware platform. I also announced the beginning of a pledge period on Kickstarter that allows anyone to take part in the first production run of commercially available Ubertooth Ones. If you would like an Ubertooth One of your own, I encourage you to consider building one or making a pledge on Kickstarter. Thank you for your support and for helping to spread the word!

Ubertooth video and news

Video of Ubertooth Zero, a preview, my talk at ToorCon 12, is now online (part 1, part 2). This includes the first public demonstration of Bluetooth sniffing with the platform. Since ToorCon, I've been working hard on Ubertooth One hardware and software. I've had to work through some production delays and errors with Ubertooth One circuit boards, but I have a good feeling about the next revision which is in production now.

I am excited to announce that my talk, Project Ubertooth: Building a Better Bluetooth Adapter has been accepted for ShmooCon 2011. This will be a longer presentation telling the complete story of the development of Project Ubertooth and demonstrating new capabilities of the platform (hopefully with working Ubertooth One prototypes). ToorCon was a preview, but ShmooCon will be the big debut.

I posted a new file release of the Ubertooth project repository tonight. This includes the new bluetooth_rxtx firmware that is starting to resemble my vision for the USB interface. The host code doesn't do much more than the ToorCon demo at this point, but quite a bit has been done to enable future enhancements.

Ubertooth: first release

Tonight I uploaded the first release of Project Ubertooth, an open source wireless development platform that can be used for Bluetooth testing and research. This is a very preliminary release, but it includes the complete hardware design for Ubertooth Zero, firmware source code, and the host code needed to perform rudimentary Bluetooth sniffing as I demonstrated at ToorCon 12. Although you can download a project archive, I recommend using the Subversion repository so that you can easily keep up to date with the project as it develops.

The documentation is still a bit thin, but there are README files scattered about the project directories. The host code can be compiled with gcc on Linux. The firmware also can be compiled with a gcc toolchain (I have found the CodeSourcery package to be helpful) and can be flashed onto a board with lpc21isp. I've been using a slightly modified SparkFun FTDI Basic Breakout for this, but there are several serial programming devices that will work with lpc21isp.

Also in the repository is an early hardware design for Ubertooth One, the next generation board that I hope to have ready within a couple months. This is a more challenging design that will probably require a few revisions, so keep your expectations low if you try to build one based on the current layout.

Ubertooth Zero, a preview

Last weekend at ToorCon 12 I unveiled Project Ubertooth, something I've been working on for more than a year. The goal of the project is to produce a low cost 2.4 GHz wireless development platform suitable for Bluetooth sniffing (among other things). If you are familiar with previous work on Bluetooth monitoring, then you know that good tools are expensive. Commercial equipment costs $10,000 or more, and even the open source solution requires a hardware investment of at least $1000.

In my talk, Ubertooth Zero, a preview, I demonstrated Bluetooth sniffing for the first time with Ubertooth Zero, my first prototype hardware model. The platform is based on the Texas Instruments CC2400 wireless transceiver paired with NXP's LPC1758, an ARM microcontroller with USB. You can build an Ubertooth Zero for less than $50 in parts. The hardware design and host code are published in the svn repository at http://ubertooth.sourceforge.net/, and firmware will follow as soon as possible (probably a couple weeks). Everything is open source.

Over the coming weeks I'll be working on the next model, Ubertooth One, which I hope to have available in early 2011. It will be compatible with the Ubertooth Zero software but will have an improved RF front end, comparable to a Class 1 Bluetooth device. I hope to produce Ubertooth One commercially, making it available to those who don't want to solder 0402s, but rest assured that the product will remain fully open source. I'm also working on firmware, host software, and documentation so that the platform will be easier to build and use.

I would love to hear from you if you decide to build an Ubertooth Zero. Keep in mind that this is a preview release with much work still undone. So far I've built three working boards, one of which fetched $275 in Sunday night's ToorCon Foundation auction, supporting technology education in developing countries. I have three more that I hope to get working soon, and then I'll start work on Ubertooth One.

So far I have implemented only single channel Bluetooth monitoring. The device sits on a single channel and receives a small subset of packets from all Bluetooth devices in range (the target devices use frequency hopping, so they only transmit a small percentage of their packets on that particular channel). This is sufficient to provide a good survey of Bluetooth activity. With some work on software in the future, the platform should be capable of hopping along with a target, receiving every packet on that piconet. Once that is working, it should be possible to use the Ubertooth platform for raw frame injection, an important capability that has been out of reach of wireless security researchers since Bluetooth's introduction. The platform could also be used for several non-Bluetooth functions such as spectrum monitoring or 802.11 FHSS

ToorCon was a blast, as always. Thanks to everyone who attended the Software Defined Radio Workshop, Real Men Carry Pink Pagers, and the Ubertooth talk. Thanks to Travis for making our talk so much fun. Thanks to Dominic for making the trip from London. Thanks to George, Tim, and David for putting on a great con and making me feel so welcome. Thanks to all the friends, both old and new. Thanks(?) to Nick et al. for embarrassing the hell out of me. Thanks to Laen for running the DorkbotPDX PCB service. Most of all, thanks to Jared Boone who couldn't be at ToorCon but who has supported my effort to develop Project Ubertooth more than anyone.