If you’ve been paying attention to the news then you might have heard of the recent Dallas tornado siren hack. Earlier in the month a hacker took control of 156 tornado warning sirens placed all around the city of Dallas, Texas in the United States. The sirens are activated via an RF control signal, and the hacker transmitted the control signal, causing all the sirens to activate causing a city wide false alarm. The attack could have been performed with a transmit capable software defined radio like the HackRF, or any other transmit capable radio such as a handheld radio.
In the blog post and video first Balint discusses the difference between a single frequency network, and a repeated network. In a single frequency network, one powerful transmitter up on a hill would be used to activate all the sirens, whereas with a repeater network several dispersed transmitters might be used to repeat the signal over a wide area.
He then discusses the difference between an analog and digital command transmission system. In an analog command transmission a simple series of tones might be used to activate the sirens. In this case the hacker could simply listen for the tones when the siren is activated during the monthly test, and save them away for a future replay attack. In a digital system instead of tones an encrypted packet of data could be used instead. Depending on how the encryption is implemented this could prevent a replay attack.
Over on YouTube a video titled “Hunting Rogue WiFi Devices using the HackRF SDR” has been uploaded. The talk is given by Mike Davis at the OWASP (Open Web Application Security Project) Cape Town. The talk’s abstract reads:
Rogue WiFi Access Points are a serious security risk for today’s connected society. Devices such as the Hak5 Pineapple, ESP8266-based ‘throwies’, or someone with the right WiFi card and software can be used to intercept users’ traffic and grab all of their credentials. Finding these rogue devices is a very difficult thing to achieve without specialised equipment. In this talk Mike will discuss the work he has been doing over the past year, to use the HackRF SDR as a RF Direction-finding device, with the goal of hunting down various malicious RF devices, including car remote jammers.
The talk starts off with the basics, explaining what the problems with WiFi devices are, what the HackRF and SDR is, and then goes on to explain some direction finding methods that Mike has been using.
Over on GitHub programmer ‘znuh’ has uploaded a new RTL-SDR compatible GNURadio based tool for DECT decoding. DECT is an acronym for ‘Digital Enhanced Cordless Telecommunications’, and is the wireless standard used by modern digital cordless phones. In most countries DECT communications take place at 1880 – 1900 MHz, and in the USA at 1920 – 1930 MHz. So in order to receive these frequencies you’ll need an RTL-SDR with an E4000 chip, or some other compatible SDR that can tune this high.
It appears that the decoder is not actually able to decode audio (at least not yet or without extra work perhaps), but it can at least output the DECT packets to Wireshark for analysis. This may be of interest to those wanting to learn more about the DECT protocol.
Update: Over on the Reddit thread for this software the original poster ‘sanjuro’ has given a hint on how to (in theory) decode the audio, he writes:
After noting down the FCC ID printed on the device, they determined that the operating frequency was 315 MHz. They discovered from the documentation that each wireless DX device is encoded with a unique code that is precoded at the factory. Only remotes with the correct code programmed in can open the door.
The first attack they tried was a simple replay attack. They used a HackRF to record the signal, and then play it back again. This worked perfectly first time.
Next they decided to take this further and reverse engineer the protocol and see if a brute force attack could be applied. By doing some logic analysis on the circuit, they were able to figure out how to iterate over the entire key space. It turns out that the lock can be brute forced in at most 14.5 hours, or 7.25 hours on average.
The Universal Radio Hacker is a software for investigating unknown wireless protocols. Features include
hardware interfaces for common Software Defined Radios
easy demodulation of signals
assigning participants to keep overview of your data
customizable decodings to crack even sophisticated
encodings like CC1101 data whitening
assign labels to reveal the logic of the protocol
fuzzing component to find security leaks
modulation support to inject the data back into the system
Inspectrum and Waveconverter are two similar programs for analyzing digital signals, however Universal Radio Hacker seems to be the most advanced.
Johannes has also uploaded four tutorial videos to YouTube which show the software in action. In the videos he uses Universal Radio Hacker to reverse engineer a wirelessly controlled power socket, and then in the last video he uses the software to transmit the reverse engineered signals via a HackRF.
OpenHAB is an open source home automation software program which is designed to interface and manage all the various sensors and systems in an automated house. One problem however, is that many wireless sensors and actuators utilize a proprietary communications protocol that is not supported by OpenHAB.
In his home, Dan Englender had several Honeywell 5800 series 345 MHz wireless security door sensors, all of which interface using a proprietary protocol that is not yet implemented in OpenHAB. In order to get around this, Dan decided to reverse engineer the protocol and implement a decoder into OpenHAB himself.
Over on YouTube the channel Budapest Hackerspace has recently uploaded a talk by Piotr Krysik which was given during the August 2016 Camp++ 0x7e0 information security conference. The talk is titled: “GSM signal sniffing for everyone with gr-gsm and Multi-RTL by Piotr Krysik” and talks about using the gr-gsm software and RTL-SDR dongles to sniff the GSM mobile phone network. Also, a tool developed by Piotr called multi-rtl which allows the proper synchronization of multiple RTL-SDR dongles in order to cover the large gap between the GSM uplink and downlink frequencies is discussed.
The talk explains a bit about how GSM works, and then goes on to talk about the gr-gsm and multi-rtl software. The talk blurb reads:
Gr-gsm is a set of tools for receiving GSM transmissions, which works with any software radio hardware capable of receiving GSM signal. Together with widely available RTL2832 based TV dongles, that are popularly used as low cost software radio receivers (known as RTL-SDR), it enables everyone to receive and study protocols used in GSM’s mobile radio interface.
Ability to receive signals spread over wide frequency range exceeding single RTL-SDR receiver’s bandwidth (~2.4MHz) was available exclusively for the owners of more capable and more expensive SDR devices. With introduction of Multi-RTL project by the author of the talk, this limit was overcome through synchronization of multiple RTL-SDR receivers in time domain, that doesn’t require complicated hardware modifications. With Muli-RTL it is possible to receive for example uplink and downlink of GSM900 transmissions, that are separated by 45MHz.
Speaker will present origins of both of the projects, together with description of their inner workings, examples of applications and plans for the future.
Recently security researcher cnxroot wrote in to let us know about two of his posts that may be of interest to readers. The posts are written in Chinese, so please use Google Translate to read them in English – it translates okay to some extent.
The first post shows us how to run the RTL-SDR on an OpenWRT capable router server. OpenWRT is a Linux firmware/OS that can be installed on several compatible router devices which extends the usefulness and features of the router. Since it is running Linux the RTL-SDR drivers can be installed onto it, and then rtl_tcp can be run, providing a remote RTL-SDR.