Wifi Satellite #34C3

Monitoring and logging the traffic of all the 14 2.4GHz channels

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We designed this device on an attempt to build a cheaper version of the Wifi Cactus using 14 ESP32 boards with OLED screens and SD card slots to display and log the 2.4GHz channels traffic.

Planning and building! 

We were all talking over Discord a few months ago and decided we should do something for the c3. Something cool to show and get in touch with people!  

We thought maybe we could do something like the Wi-Fi Cactus from DEFCON:

It's made out of Hak5's WiFi Pineapples to sniff as much WiFi traffic as possible!

I said that we could do the same thing just with ESP's! We are all students, so it  had be cheap, DIY and open source.  

I already made the ESP8266 PacketMonitor before. It shows the Wi-Fi traffic from one channel on a little OLED display.

Perfect for our idea, only one problem... the ESP8266 is only able to sniff the packet header :(
To capture full packets, we needed the more powerful successor: Espressif’s ESP32!  

Good that I was already in contact with Travis Lin to make a new PacketMonitor board using  the ESP32!

We had a few problems making both the hardware and the software and it took a while…

But now we have this great and inexpensive development board with a 1.3" OLED, SD card slot, LiPo charger and the new ESP32 WROVER module with extra RAM:

It comes with the PacketMonitor32 software I’ve made:  

I told Travis about our plans and he was kind enough to sponsor us 14 of his new boards!  

(one for every 2.4GHz WiFi channel)

Because the board already had everything we needed, we only had to think of how to power it, where to get 14 micro SD cards and how we would mount all these boards.  

Deantonious, our master of design, had the idea to put them on a stick, so it would look like the solar shield of a satellite (that's why the name *WiFi Satellite*). He designed the 3D parts and printed them.  

We had many ideas on how to save the whole traffic, but the easiest was to use a micro SD card for every module. That way we wouldn't need a master device and save us a lot of time programming and debugging.

I tested different SD cards and ended up buying 16 GB SanDisk cards from AliExpress (around 6,90€ each). We could have got cheaper cards, but we needed something with enough storage and a good speed.

We also bought USB cables for each board (good thing they cost only a few cents from China) and I was lucky enough to find 2 very good 7 port USB hubs for just 10€.  

We wanted to use 18650 LiPo cells to make the whole thing portable and I had a lot of cells from old laptop battery packs.

I found these 18650 power bank adapters on AliExpress and bought one for every board.

Everything seemed to work fine until I made a stresstest...

they lasted for a few hours (around what I expected) but when I wanted to charge them, two of the power banks started smelling like burned electronics.

It turned out that the batteries were fine, but the charger chip was burned for some reason.

Seemed like these power bank adapters weren't that great after all. Maybe fake charger chips, maybe just two faulty units, maybe they just weren't protected like they claimed on the website.

Anyway, I decided to stop using them. LiPo batteries are not things you want to be around, if they start burning (or worse).

So at the end we kept our WiFi Satellite safe and stationary and it worked just fine! :)

Standard Tesselated Geometry - 152.72 kB - 12/28/2017 at 14:27


Standard Tesselated Geometry - 265.12 kB - 12/28/2017 at 14:20


Standard Tesselated Geometry - 35.14 kB - 12/28/2017 at 14:20


  • Funny LED colors ¯\_(ツ)_/¯

    deantonious01/04/2018 at 16:08 2 comments

    A few hours past until we noticed the LED colors from the right side were different from the left ones.

    The LEDs are on the back side of the modules and indicate if the LiPo battery (if one is connected) is charging (red) or fully charged (green).

    It looked a bit too strange to just be something random.

    We were trying to find out what was causing this color change, when @davedarko helped us realize that it could be caused by the different power supplies we were using.

    We used two 7-port USB hubs to power all 14 boards. The left side was using the original 5V 2A power supply of the hub, while the right ones were using a USB cable connected to a 2.4A charger (the original power supply broke weeks before).

    We now think that the USB hub does not support that much current over the USB connection, because that is usually just for transmitting data and you got a seperate connector for supplying power.

    That may caused a low voltage output on the USB connections (below 4.2V) and the boards to think that they have to charge their batteries.

    But there were no batteries connected and even if there were, why would the power supply voltage matter since the batteries have a different voltage(?)...

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