Tagged: security

Student Arrested in Taiwan for using SDR and Handheld Radios to Halt Four High Speed Trains with TETRA Hack

The Taipei Times has reported that a 23-year-old university student in Taiwan has been arrested after using a software-defined radio and hand held radio to hack into Taiwan High Speed Rail Corporation's (THSRC) internal radio communications and halt four trains mid-service.

Chinese-language coverage from UDN and Newtalk fills in some details omitted in the English Taipei Times article. The system the student compromised is TETRA, and at 23:23 on April 5, 2026, the student transmitted a "General Alarm" (GA) signal, the highest-priority TETRA alert, which automatically instructs trains in the area to switch to manual emergency braking. Four trains were stopped for 48 minutes. THSRC's radio system has reportedly been in service for 19 years with seven verification layers, but parameters were apparently never meaningfully rotated over that period.

Police describe the suspect as buying an SDR online, connecting it between an antenna and a laptop, capturing THSRC traffic, and decoding the relevant parameters in software, then programming those parameters into one of his eleven handheld radios. A 21-year-old friend also allegedly supplied some critical THSRC parameters. The actual details of the 'hack' aren't entirely clear from the news articles. We suspect that the THSRC TETRA system is simply unencrypted, and that the student was able to spoof a legitimate signal. It's also possible that the THSRC TETRA system used TEA1 encryption, which is known to be broken. 

Police located the student through a combination of network-side TETRA logs and CCTV. When the THSRC control center called back to verify the alarm, the person on the other end gave contradictory answers and then powered the radio off, prompting THSRC to audit their handheld fleet, confirm every issued radio was accounted for in its storage locker, and report to police that the parameters had been cloned.

Base station logs from the THSRC TETRA infrastructure (which record which sites received the uplink, with multi-site signal strength narrowing the origin) were used to localize the transmission source, and CCTV from around the coverage area was then used to identify the student and trace him to his rental unit. Search warrants on 28 April seized 11 handheld radios, a laptop, and the SDR. 

He is currently out on NT$100,000 (3,200 USD) bail and faces up to ten years under Taiwan's Railway Act and Criminal Code, with an unconvincing "had it in my pocket and accidentally pressed the button" defense.

Stories like this are a reminder that experimenting with operational safety-of-life radio systems carries serious legal consequences. Back in 2016, we covered the case of Dejan Ornig, a Slovenian university student who used an RTL-SDR and the open source Osmocom TETRA decoder to discover that his country's police TETRA terminals were running unauthenticated, despite official documents stating otherwise. After seven years of court hearings, he ended up with a seven-month suspended sentence. More recently, we posted on the End of Train (EoT) vulnerability, where a security researcher demonstrated that an SDR can replicate the unauthenticated braking command on US freight trains.

The Equipment Seized by Police
The Equipment Seized by Police
A Taiwanese High Speed Train (Source: https://en.wikipedia.org/wiki/File:THSR_700T_TR17_20130907.jpg)
A Taiwanese High Speed Train (Source: https://en.wikipedia.org/wiki/File:THSR_700T_TR17_20130907.jpg)
Translated news graphic from https://udn.com/news/story/7315/9475450
Translated news graphic from https://udn.com/news/story/7315/9475450
 

Detecting Hidden GPS Trackers via Electromagnetic Unintentional Emissions with a HackRF

Researchers from Hunan University, Boise State, and UT Arlington have published a paper called "GPSBuster" (PDF link), demonstrating how a HackRF One can sniff out covert GPS trackers by their unintended electromagnetic radiation. Hidden trackers are hard to find since they only receive satellite signals and may store coordinates locally rather than transmit. Instead of looking for transmissions, GPSBuster targets side-channel leakage from the tracker's mixed-signal SoC, specifically the coupling between the quartz oscillator, local oscillator, and mixer used to downconvert the 1575.42 MHz L1 signal.

The team found that an active tracker leaks two characteristic spectra: a low band around 26 to 104 MHz and a high band around 1545 to 1625 MHz, each with a strong peak and evenly spaced harmonics. The low band reflects coupling between the quartz oscillator (typically 26 MHz) and the IF, while the high band contains LO plus IF spacing that always sums to 1575.42 MHz, giving a database-free detection rule. The setup consists of a HackRF, an NFP-3 near-field probe, and a 35 dB LNA. The use of the near-field probe means that sweeping the probe over an area to find the tracker is necessary, and the maximum detection range was 0.61 m.

Tested against the top 10 trackers available on a popular online marketplace, GPSBuster hit a 98.4% detection rate, working through plastic, cotton, canvas, and leather, and alongside phones, laptops, and speakers. It also extended to L1+L5 modules like the Quectel LC29H series, and even metal-shielded chips still leaked enough via PCB traces to be picked up.

Covert GPS Tracker Detection with a HackRF and Near Field Probe
Covert GPS Tracker Detection with a HackRF and Near Field Probe
GPSBuster Field Prototype
GPSBuster Field Prototype

DeDECTive: A DECT 6.0 Cordless Phone Scanner and Voice Decoder for the HackRF

Over on GitHub and YouTube, we've seen the release of Sarah Rose's new program called DeDECTive, a DECT 6.0 scanner and voice decoder for the HackRF running on Linux systems. DECT (Digital Enhanced Cordless Telecommunications) is a digital wireless protocol typically used by modern cordless phones.

Back in 2019, Sarah (previously known as Corrosive) demonstrated how to use gr-dect2 to decode DECT in a previous video. In her latest work, she's ported gr-dect2 to C++ and written a nice GUI for the decoder. This makes running and setting up the decoder a significantly better experience. The GUI has a wideband scanner and the ability to tune for a single DECT channel for full voice decoding. There is also a CLI version that will automatically tune to the first active voice channel.

We note that many DECT cordless phones use encryption, so this software may not work with those devices. In any case, please be aware that intercepting phone calls may be illegal in many jurisdictions.

DeDECTive: The DECT Toolkit

ESP32 Bus Pirate: Update Brings Waterfall Displays, Cellular Modem Support and External Radio Expander

Back in September 2025, we posted about the "ESP32 Bus Pirate" firmware, which transforms an ESP32-S3 into a multi-protocol debugging and hacking tool. Although the ESP32 does not have true SDR capabilities, it can leverage its numerous built-in radio hardware components to achieve a range of interesting feats. Recently, "Geo," the creator of the ESP32 Bus Pirate, wrote in to share some recent firmware updates with us. He writes:

The ESP32-Bus-Pirate project is an open-source firmware that transforms inexpensive ESP32-S3 boards into versatile hardware hacking and debugging tools. Inspired by tools like the Bus Pirate and Flipper Zero, the firmware allows a single ESP32 device to interact with a wide range of digital buses, radios, and hardware interfaces.

Because ESP32 boards include integrated WiFi and Bluetooth radios and can interface with many external modules, the firmware makes it possible to experiment with both hardware protocols and RF systems using very low-cost hardware.

The firmware currently supports a wide range of protocols and devices including:

I²C, SPI, UART, CAN, 1-Wire, infrared, smartcards, Sub-GHz radios, RF24 modules, WiFi, Bluetooth and cellular modems.

Major New Features in v1.5

The latest release adds several major capabilities useful for hardware analysis and RF experimentation.

Waterfall Spectrum Displays

Multiple RF modules can now display real-time waterfall visualizations, showing signal peaks and activity across frequencies. This is available for:

• Sub-GHz radios
• RF24 modules
• FM radio modules
• WiFi channel activity

This makes it easier to visually monitor RF environments directly from the device.

Sub-GHz Improvements

The Sub-GHz subsystem has been completely reworked for improved reliability when recording, replaying and receiving RF frames. Raw payload transmission is also supported.

Cellular Modem Support

ESP32-Bus-Pirate can now interact with cellular modem modules, allowing users to inspect modem and network information and perform operations such as:

• Dumping SIM card data
• sending SMS
• dialing calls

External Radio Expander

The firmware now supports an **external UART radio expansion module** called the **ESP32 Bus Expander**, which allows adding additional RF hardware modules to the system, notably for the WiFi 5GHz.

Links

Project:
https://github.com/geo-tp/ESP32-Bus-Pirate

Web Flasher:
https://geo-tp.github.io/ESP32-Bus-Pirate/webflasher/

Documentation:
https://github.com/geo-tp/ESP32-Bus-Pirate/wiki

Scripts collection:
https://github.com/geo-tp/ESP32-Bus-Pirate-Scripts

ESP32 Bus Expander:
https://github.com/geo-tp/ESP32-Bus-Expander

ESP32 Bus Pirate. Left - Running on COTS ESP32-S3 based devices. Right - ESP32 Bus Pirate Interface
ESP32 Bus Pirate. Left - Running on COTS ESP32-S3 based devices. Right - ESP32 Bus Pirate Web Interface

Exploring the Privacy Risks of Tire Pressure Monitoring Systems with RTL-SDR

Tire Pressure Monitoring System (TPMS) privacy concerns are a topic that comes up every now and then. Most modern vehicles have wireless tire pressure sensors that communicate with the vehicle's computer to alert the driver when tire pressure falls below a safety threshold.

The privacy issue is that these TPMS sensors each transmit a unique identifier, so the computer can know which tire is being measured, and not read other vehicles' sensors by mistake. As TPMS is not encrypted in any way, anyone with an RTL-SDR or other similar radio can receive and decode TPMS messages, including the unique identifier. This raises privacy concerns as this can be used to log the presence and movement of individual vehicles. 

A recent academic paper by university researchers showed how researchers deployed simple RTL-SDR + Raspberry Pi-based receivers along a road over a period of 10 weeks. They showed that TPMS transmissions can not only be used to identify, track, and detect the presence and daily routines of individual vehicles, but also to determine the type and weight of the vehicle via pressure readings.  Interestingly, they also note that variations in the weight of an identified vehicle could indicate, for example, whether a truck is loaded or unloaded, or whether there are additional passengers in a car.

The researchers highlight privacy concerns, noting that such data could be collected and sold by data mining companies without the driver's knowledge. 

RTL-SDR + Raspberry Pi for TPMS Monitoring
RTL-SDR + Raspberry Pi for TPMS Monitoring
The TPMS Monitoring Setup
The TPMS Monitoring Setup

Telive osmo-tetra-sq5bpf: An Experimental TETRA Decoder that Enables Voice Decryption (If You Have the Key)

Thank you to Jacek / SQ5BPF for letting us know that he's recently released a modified version of the Telive TETRA decoder for Linux. The modification allows the user to listen to TEAx-encrypted voice signals if they have the decryption key. Typically, if a TETRA signal is encrypted, there is no way to listen to it, unless you have obtained the decryption key from the network operator, or extracted it from TETRA keyloader hardware.

But because the TEA1 encryption was broken due to a backdoor being discovered in 2023, he has also added support for using the 32-bit short key directly, which can be automatically recovered from TETRA traffic using his other software called teatime. TEA1 encryption is being phased out, but many deployments still use it.

The software is designed for advanced users to compile and run, so very little documentation is provided. However, there is a blog post here that explains the overall steps. Some additional information can be found on SQ5BPF's RadioReference post here.

TETRA Decoding (with telive on Linux)
TETRA Decoding (with telive on Linux)

The Thought Emporium Explores IMSI Cell Phone Tracking and Other Advanced Cell Phone Attacks with Software Defined Radios

Over on YouTube, The Thought Emporium channel has uploaded a video outlining how mobile phones constantly leak unique IMSI identifiers over the air, making passive location tracking much easier than most people expect. While LTE and 5G improve security, older 2G and 3G protocols still expose permanent subscriber IDs that can be collected and linked to movement over time.

The video highlights how accessible this surveillance is. A cheap RTL-SDR USB dongle, basic antenna, and free software pre-installed on DragonOS are enough to passively collect IMSI numbers from nearby phones running on 3G. Once you know a person's unique IMSI number, you can easily track their movements if you have cheap radios monitoring the areas they frequent.

They also show how it's possible to use a more advanced TX-capable SDR like a USRP B210 to create a Stingray device, which is a fake cell-tower base station that you can force nearby cell phones to connect to. Once connected to the Stingray, all communications from your phone can be tapped. Finally, they discuss SS7 attacks, which, while difficult and/or expensive to gain access to the SS7 walled garden, can allow malicious actors to easily reroute security-related messages, such as 2-factor authentication.

The video finishes with potential defenses, including turning phones off when needed, forcing more secure LTE/5G-only connections, and using tools that detect fake cell towers. Privacy-focused mobile services that rotate identifiers are also discussed.

Recreating ICE Spy Tech Was WAY Too Easy

 

A Discussion on How WiFi Can Be Used To See Through Walls

Earlier in the year on YouTube, Yaniv Hoffman and Occupy The Web haved discussed research showing how Wi-Fi signals can be used to detect and track people through walls. The idea is simple from an RF point of view. Wi-Fi is just radio, and when those signals pass through a room they reflect and scatter off walls, furniture, and human bodies. By analyzing these reflections, it is possible to infer movement and even rough human outlines without placing any hardware inside the room.

Using low-cost SDRs, a standard PC, an NVIDIA GPU, and open-source AI tools like DensePose, researchers can reconstruct basic 3D human shapes in real time. In some cases, the system does not even need to transmit its own signal. It can passively analyze reflections from an existing Wi-Fi router already operating in the home.

The speakers note that this raises obvious privacy concerns. While there are some benign uses like motion-based home security or monitoring breathing in elderly care, the same techniques could be misused. Countermeasures are limited, as Wi-Fi uses spread spectrum techniques that make jamming difficult. 

If you're interested, we posted about something similar in 2015, where USRP radios were being used to detect the presence of people behind walls.

They’re Watching You Through Wi-Fi… And You Have No Idea