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Wireless security monitoring in the 2.4 GHz spectrum often depends on active probing, which can not only make the monitoring infrastructure vulnerable to attackers but also clutter the radio frequency environment. On the other hand, taking a passive approach by listening without transmitting allows security teams to detect malicious wireless activity more discreetly and reliably.

To put this idea into practice, the project Travel WiFi Canary was developed. This system serves as an early-warning mechanism using ESP32 microcontrollers. By operating the Wi-Fi radio in promiscuous mode, the device passively captures raw IEEE 802.11 management frames and traffic patterns. This helps identify potential threats such as deauthentication attacks, beacon spam, rogue access points often referred to as Evil Twins, and unauthorized probe requests. Eventually, it provides comprehensive insights into the wireless environment, enabling you to act proactively rather than reactively.

In this article, we will guide you through configuring, flashing, and running Travel WiFi Canary on the LilyGo T3 V1.6.1 development platform. Let’s get rolling!

What is Travel WiFi Canary?

The Travel WiFi Canary is a project that turns a low-cost ESP32 microcontroller into a passive 2.4 GHz threat-detection device. It operates continuously by alternating between active network enumeration and passive promiscuous packet capturing across specified channels.

At its core, the device’s Wi-Fi chip listens directly to raw radio signals passing through the air rather than connecting to a specific network.

When a wireless signal arrives, a fast automated responder checks the basic structure of the incoming data instantly. It identifies network management signals, such as connection requests, disconnection commands, or nearby network announcements, and separates them from standard web traffic.

To handle intense bursts of wireless activity without getting overwhelmed or missing crucial information, the chip places these flagged security signals into a temporary holding queue. This allows the main system to process and analyze the data safely in the background while keeping the hardware radio free to capture new incoming signals without interruption.

The central intelligence of the project relies on a dynamic confidence-scoring engine rather than rigid binary alerts. As the system processes the ring queues and periodic active scans, it evaluates detected anomalies against a local memory table built during the startup baseline phase.

Active scans check nearby Access Points for structural security violations. If an Access Point using an encrypted baseline protocol like WPA2 or WPA3 is detected operating without encryption, the system identifies an open clone attack. Security downgrades, unexpected vendor prefix mismatches on familiar SSIDs, or sudden disappearances of legitimate Access Points during an active open broadcast instantly contribute points to the global confidence score.

Simultaneously, the passive sniffer thread drains the lock-free queues to detect airborne attacks. Deauthentication frame floods are monitored over rolling time windows, assigning score penalties if threshold limits are breached by single sources or broadcast addresses.

The sniffer also inspects the payload fields inside beacon frames to detect Pwnagotchi signatures, parsing JSON structures hidden in vendor tags to determine if the device is operating in an active attack state.

All calculated points feed into a unified state machine. Aggregate scores between zero and two keep the device in a normal state, scores between three and five push it into a caution state, and scores of six or higher escalate the device into an active alert state.

To prevent temporary radio noise or brief packet anomalies from causing permanent alarm states, a background timer executes a score decay routine every minute. This routine gradually reduces the aggregate threat score over time, allowing the system to automatically transition back to a normal state once threat vectors clear the area. Hardware outputs, such as status LEDs or connected display controllers, continuously mirror the internal state variable to provide real-time visual monitoring.

What is LilyGo T3 V1.6.1?

The Travel WiFi Canary was initially made for the M5Stack Atom Lite development board. However, in this demonstration, I will test it on the LilyGo T3 V1.6.1.

The LilyGo T3 V1.6.1, also called the TTGO T3 LoRa32 V1.6.1, is an open-source development board designed for Internet of Things (IoT) projects and long-range RF communication. It has an ESP32 chip that allows for packet sniffing and Wi-Fi scanning. It gives us all the necessary functionality for wireless threat detection required by the Travel WiFi Canary project.

Getting Started with Travel WiFi Canary

The best way to flash the Travel WiFi Canary is by using Visual Studio Code along with the PlatformIO IDE extension. The installation process is fairly simple, so let’s move on to the next step, which is cloning the repository. I will use the modified version designed for the LilyGo T3 device. Here’s the command to do that:

kali> git clone https://github.com/AirClick-Code/esp32-wifi-canary.git

Next, connect your LilyGo T3 V1.6.1 to your computer using a data-capable Micro-USB cable. In Visual Studio Code, click on the PlatformIO status bar at the bottom and select env:esp32dev. Then, you can either click the checkmark icon in the status bar or press Ctrl+Alt+B to compile the firmware.

Once that is complete, click the right arrow icon in the status bar to start the upload process. PlatformIO will automatically detect the serial port, trigger the ESP32 to enter bootloader mode via auto-reset circuitry using the DTR and RTS lines, erase the necessary flash sectors, and upload the binaries seamlessly.

After the upload is complete, you can monitor the device with the built-in command:

pio device monitor -b 115200

At this point, the state machine and scanning engine are fully operational. During its initial scan, it detected seven nearby access points, recording their SSIDs, BSSIDs, signal strengths, channels, and encryption methods in memory.

Now, let’s simulate an open clone of a known encrypted network. The README file provides the following instructions:

I created a Wi-Fi access point from my phone with the same name as the network to which my system is connected, but without a password. Let’s observe how the WiFi Canary responds.

The script successfully identified the clone and granted 4 points to the score, changing the state to caution. The rogue open clone remained active in the following 20-second scan with a strong RSSI, adding another 4 points, which brought the total score to 8 and changed the state to alert. At the 310-second mark, the decay timer activated, decreasing the score from 8 to 7. However, since the score remained above the SCORE_ALERT threshold of 6 or higher, the system continued to maintain its alert state until the threat was resolved and the score naturally decayed back to zero.

Limitations

Despite the benefits of confidence scoring in reducing unexpected alerts, the possibility of false positives still exists. This is particularly true in enterprise networks, multi-node mesh setups, and crowded public venues, which can display behaviors that resemble attack patterns. On the flip side, false negatives may arise if a skilled attacker impersonates a legitimate BSSID while carefully adjusting their transmission power to fit in with normal signal strength variations, thus evading detection.

The limitations of the physical hardware create additional coverage boundaries. Passive detection of deauthentication relies heavily on the distance from the receiving device, meaning that low-power or far-off transmitters may be beyond the reach of the antenna. Furthermore, monitoring is confined solely to the 2.4 GHz spectrum, leaving the 5 GHz and 6 GHz bands completely unmonitored.

Lastly, the design of the radio architecture leads to a temporary gap in scanning whenever the chip switches between promiscuous packet sniffing and active environment scanning, resulting in a three-second blind spot where airborne deauthentication bursts can go unnoticed.

Summary

For many travelers and remote workers, understanding whether the Wi-Fi around them is secure is crucial. Private messages and sensitive information can be easily compromised when malicious actors set up fake hotspots or disrupt local connections. A device like the Travel WiFi Canary can continuously monitor the airwaves and alert you the moment a wireless attack is detected.

This device uses active Wi-Fi scanning and passive signal listening to find threats in real time. It constantly checks nearby networks against a trusted standard to spot fake open hotspots, duplicate routers, or security issues. At the same time, it listens for harmful activities like deauthentication attacks or rogue scanning tools. When it detects a threat, it raises a danger level with an internal scoring system and triggers a clear visual alarm. This alerts you immediately, giving you a warning before your devices may face any risk.

If you’re interested in improving your knowledge of wireless security, take a look at our Wi-Fi Hacking training. This course will guide you on how to assess the security of wireless networks and equip you with modern strategies to protect them effectively.

The post Building a Pocket Wi-Fi Threat Detector first appeared on Hackers Arise.