Category: HackRF

Exploring the Limits of General Purpose SDR Devices

Back in August 2019 the Chaos Communication Camp was held in Germany. This is a 5 day conference that covers a variety of hacker topics, sometimes including SDR. At the conference Osmocom developer Harald Welte (aka @LaF0rge) presented a talk titled "The Limits of General Purpose SDR devices". The talk explains how general purpose TX capable SDRs like HackRFs and LimeSDRs have their limitations when it comes to implementing advanced communications systems like cellular base stations.

If you prefer, the talk can be watched directly on the CCC website instead of YouTube.

Why an SDR board like a USRP or LimeSDR is not a cellular base station

It's tempting to buy a SDR device like a LimeSDR or USRP family member in the expectation of operating any wireless communications system out there from pure software. In reality, however, the SDR board is really only one building block. Know the limitations and constraints of your SDR board and what you need around it to build a proper transceiver.

For many years, there's an expectation that general purpose SDR devices like the Ettus USRP families, HackRF, bladeRF, LimeSDR, etc. can implement virtually any wireless system.

While that is true in principle, it is equally important to understand the limitations and constraints.

People with deep understanding of SDR and/or wireless communications systems will likely know all of those. However, SDRs are increasingly used by software developers and IT security experts. They often acquire an SDR board without understanding that this SDR board is only one building block, but by far not enough to e.g. operate a cellular base station. After investing a lot of time, some discover that they're unable to get it to work at all, or at the very least unable to get it to work reliably. This can easily lead to frustration on both the user side, as well as on the side of the authors of software used with those SDRs.

The talk will particularly focus on using General Purpose SDRs in the context of cellular technologies from GSM to LTE. It will cover aspects such as band filters, channel filters, clock stability, harmonics as well as Rx and Tx power level calibration.

The talk contains the essence of a decade of witnessing struggling SDR users (not only) with running Osmocom software with them. Let's share that with the next generation of SDR users, to prevent them falling into the same traps.

The Limits of General Purpose SDR devices

Using a HackRF SDR to Sniff RF Emissions from a Cryptocurrency Hardware Wallet and Obtain the PIN

At last years Chaos Communication Congress (35C3) Conference, leveldown security presented their findings on multiple security vulnerabilities present in cryptocurrency hardware wallets.  Cryptocurrency is a type of digital asset that relies on computers solving cryptographic equations to keep the network trusted and secure. Popular cryptocurrencies include Bitcoin, Ethereum and Ripple. To access your cryptocurrency funds on a computer, a software application called a wallet is used.

However, if a computer holding a wallet is compromised, it is possible that the wallet could be opened by a hacker and funds transferred out. To improve security, hardware wallets are available. These are USB keys that require you to enter a PIN on the key before the funds can be accessed. If the USB key is not inserted and activated by the PIN, the wallet cannot be opened.

All electronic devices including hardware cryptocurrency wallets unintentionally emit RF signals. One possible attack against a hardware wallet is to analyze these RF emissions and see if any information can be obtained from them.  The team at leveldown found that the Ledger Blue cryptocurrency wallet in particular has a flaw where each PIN number button press emits a strong RF pulse. By using a HackRF and machine learning to analyze the unintentional RF output of each button press, the team was able to retrieve the PIN number with only RF sniffing from more than 2 meters away.

To do this they created a GNU Radio flowchart that records data from the HackRF whenever an RF pulse is detected. A small Arduino powered servo then presses the buttons on the wallet hundreds of times, allowing hundreds of RF examples to be collected. Those RF samples are then used to train a neural network created in Tensorflow (a popular machine learning package). The result is a network that performs with 96% accuracy.

If you're interested in exploring other unintentional RF emissions from electronics, check out our previous post on using the TempestSDR software to spy on monitors/TVs with unintentionally emitted RF, and the various other posts on our blog on this topic.

Andreas Spiess Explains Software Defined Radio in YouTube Video

Over on YouTube Andreas Spiess has uploaded a video titled "How does Software Defined Radio (SDR) work under the Hood?". The video is an entertaining introduction to how software defined radio works and begins from the beginning by explaining how basic analogue radios work with components such as modulators, demodulators, frequency generators, mixers and filters. After the basics he goes on to explain the digitization of radio signals that occurs in SDRs, and gives an introduction ADCs and how IQ sampling works.

Later in the video Andreas shows various applications for SDRs, discusses various SDRs on the market like RTL-SDR, HackRF, SDRplay, LimeSDR and PlutoSDR and introduces GNU Radio Companion and other SDR programs from our big list of software post.

How does Software Defined Radio (SDR) work under the Hood?

Using a Drone and HackRF to Inject URLs, Phish For Passwords on Internet Connected TVs by Hijacking Over the Air Transmissions

There is nothing wrong with your television set. Do not attempt to adjust the picture. We are controlling transmission.

At this years Defcon conference security researcher Pedro Cabrera held a talk titled  "SDR Against Smart TVs; URL and channel injection attacks" that showed how easy it is to take over a modern internet connected smart TV with a transmit capable SDR and drone. The concept he demonstrated is conceptually simple - just broadcast a more powerful signal so that the TV will begin receiving the fake signal instead. However, instead of transmitting with extremely high power, he makes use of a drone that brings a HackRF SDR right in front of the targets TV antenna. The HackRF is a low cost $100-$300 software defined radio that can transmit.

Title Slide from the Defcon 27 Talk: SDR Against Smart TVs; URL and channel injection attacks.
Title Slide from the Defcon 27 Talk: SDR Against Smart TVs; URL and channel injection attacks.

While the hijacking of TV broadcasts is not a new idea, Pedro's talk highlights the fact that smart TVs now expose significantly more security risks to this type of attack. In most of Europe, Australia, New Zealand and some places in Western Asia and the Middle East they use smart TV's with the HbbTV standard. This allows for features like enhanced teletext, catch-up services, video-on-demand, EPG, interactive advertising, personalisation, voting, games, social networking, and other multimedia applications to be downloaded or activated on your TV over the air via the DVB-T signal.

The HbbTV standard carries no authentication. By controlling the transmission, it's possible to display fake phishing messages that ask for passwords and transmit the information back over the internet. A hacker could also inject key loggers and install cryptominers.

Recorded talks from the Defcon conference are not up on YouTube yet, but Wired recently ran a full story on Pedros talk, and it's worth checking out here. The slides from his presentation can be found on the Defcon server, and below are two videos that show the attack in action, one showing the ability to phish out a password. His YouTube channel shows off several other hijacking videos too.

SDR Against Smart TVs: Drones carrying SDRs

SDR Against Smart TVs: Social engineering


SDRTrunk 0.4.0 Alpha 9 Updates Highlighted

You may recall that a few years ago we released a tutorial on how to set up and use [SDRTrunk]. Fast forward a few years and the software has seen numerous changes. This application was designed primarily for tracking trunking radio systems but also has the ability to decode things like MDC-1200, LoJack and more.

The software is compatible with many Software Defined Radios such as our RTL-SDR v3, HackRF and the Airspy. Some of the newer improvements include a bundled copy of java so that an installation of java is not required on the host computer, as well as decoding improvements for P25 among other digital voice modes. You can find a full list of improvements along with the latest release on [GitHub]

The biggest feature many have been waiting for is the ability to import talk groups for their radio system into the application from radio reference. While this has not yet been implemented, user [Twilliamson3] has created a [web application] that will convert table data from radio reference into a format that is supported by SDRTrunk.

SDRTrunk Screenshot
SDRTrunk Screenshot

Running a Tesla Model 3 on Autopilot off the Road with GPS Spoofing

Regulus is a company that deals with sensor security issues. In one of their latest experiments they've performed GPS spoofing with several SDRs to show how easy it is to divert a Tesla Model 3 driving on autopilot away from it's intended path. Autopilot is Tesla's semi-autonomous driving feature, which allows the car to decide it's own turns and lane changes using information from the car's cameras, Google Maps and it's Global Navigation Satellite System (GNSS) sensors. Previously drivers had to confirm upcoming lane changes manually, but a recent update allows this confirmation to be waived.

The Regulus researchers noted that the Tesla is highly dependent on GNSS reliability, and thus were able to use an SDR to spoof GNSS signals causing the Model 3 to perform dangerous maneuvers like "extreme deceleration and acceleration, rapid lane changing suggestions, unnecessary signaling, multiple attempts to exit the highway at incorrect locations and extreme driving instability". Regarding exiting at the wrong location they write:

Although the car was a few miles away from the planned exit when the spoofing attack began, the car reacted as if the exit was just 500 feet away— slowing down from 60 MPH to 24 KPH, activating the right turn signal, and making a right turn off the main road into the emergency pit stop. During the sudden turn the driver was with his hands on his lap since he was not prepared for this turn to happen so fast and by the time he grabbed the wheel and regained manual control, it was too late to attempt to maneuver back to the highway safely.

In addition, they also tested spoofing on a Model S and found there to be a link between the car's navigation system and the automatically adjustable air suspension system. It appears that the Tesla adjusts it's suspension depending on the type of road it's on which is recorded in it's map database.

In their work they used a ADALM PLUTO SDR ($150) for their jamming tests, and a bladeRF SDR ($400) for their spoofing tests. Their photos also show a HackRF.

Regulus are also advertising that they are hosting a Webinar on July 11, 2019 at 09:00PM Jerusalen time. During the webinar they plan to talk about their Tesla 3 spoofing work and release previously unseen footage.

GPS/GNSS spoofing is not a new technique. In the past we've posted several times about it, including stories about using GPS spoofing to cheat at Pokémon Go, misdirect drivers using Google Maps for navigation, and even a story about how the Russian government uses GPS spoofing extensively.

Some SDR tools used to spoof the Tesla Model 3.
Some SDR tools used to spoof the Tesla Model 3.

Hak5: Hacking Ford Key Fobs with a HackRF and Portapack

This weeks episode of Hak5 (an information security themed YouTube channel) features Dale Wooden (@TB69RR) who joins hosts Shannon and Darren to demonstrate a zero day vulnerability against Ford keyless entry/ignition. More details about the vulnerability will be presented at this years DEF CON 27 conference, which is due to be held on August 8 - 11.

In the video Dale first demonstrates how he uses a HackRF with Portapack to capture and then replay the signal from a Ford vehicle's keyfob. The result is that the original keyfob no longer functions, locking the owner out from the car. After performing a second process with another keyfob, Dale is now able to fully replicate a keyfob, and unlock the car from his HackRF.

Dale explains that unlike the well known jam-and-replay methods, his requires no jamming, and instead uses a vulnerability to trick the car into resetting the rolling code counter back to zero, allowing him to capture rolling codes that are always valid. Dale also notes that he could use any RX capable SDR like an RTL-SDR to automatically capture signals from over 100m away.

The vulnerability has been disclosed to Ford, and the full details and code to do the attack will only be released at DEF CON 27, giving Ford enough time to fix the vulnerability. It is known to affect 2019 Ford F-150 Raptors, Mustangs and 2017 Ford Expeditions, but other models are also likely to be vulnerable.

The video is split into three parts. In part 1 Dale demonstrates the vulnerability on a real vehicle and in part 2 he explains the story behind his discovery, how he responsibly disclosed the vulnerability to Ford and how to reset the keyfob yourself. Finally in part 3 Darren interviews Dale about his experiences in the RF security field.

Dales discovery has also been written up in an article by The Parallex which explains the exploit in more detail.

Hacking Ford Key Fobs Pt. 1 - SDR Attacks with @TB69RR - Hak5 2523

Hacking Ford Key Fobs Pt. 2 - SDR Attacks with @TB69RR - Hak5 2524

Hacking Ford Key Fobs Pt. 3 - SDR Attacks with @TB69RR - Hak5 2525

SignalsEverywhere: What SDR To Buy? Choose the Right one For You

Over on his YouTube channel SignalsEverywhere, Corrosive has just released a new video titled "Software Defined Radio Introduction | What SDR To Buy? | Choose the Right one For You". The video is an introduction to low cost software defined radios and could be useful if you're wondering which SDR you should purchase.

The video includes a brief overview of the Airspy, KerberosSDR, PlutoSDR, LimeSDR Mini, HackRF, SDRplay RSPduo and various RTL-SDR dongles. In addition to the hardware itself Corrosive also discusses the compatible software available for each SDR.

Software Defined Radio Introduction | What SDR To Buy? | Choose the Right one For You