You started 2018 thinking about your privacy. You glance at your phone on the table, and though you're not ready to give it up, you feel you could do more to prevent leaks than just updating your operating system and practicing good discipline. The most extreme approach is to keep it in a Faraday box. The market offers portable solutions, but the effective ones are expensive. That's where the DIY world comes in.
What a Faraday Box Really Is
One of the first things to understand about Faraday boxes is that they aren't perfect. If you imagine a kind of absolute electromagnetic vacuumyou're in for disappointment. The idea is to attenuate enough energy to protect a device (an electromagnetic pulse comes to mind) or to make life difficult for anyone trying to connect to it. There are also important differences in what you're trying to achieve. With an electromagnetic pulse, the affected frequencies depend on the source, but for phones, we care about blocking GSM, WiFi, Bluetooth, NFC, and GPS.
What You'll Need
The generic instructions for building a Faraday box follow (more or less) the same line. You'll need:
- One or two boxes. The number changes the final design. If one, something like a shoebox with a lid is recommended; if two, one box should fit snugly inside the other.
- Aluminum foil. Many enthusiasts choose aluminum tape for better control, though it requires more experimentation, and not all tapes are suitable.
- Scissors or a cutter, and a ruler (optional). The aluminum surfaces shouldn't have odd gaps or slots, so cuts need to be good and clean.
- Patience. A Faraday box is supposed to be buildable in under twenty minutes, but nobody is rushing you here. Take your time.
Two Example Designs
We actually have more room to maneuver and improvise than we imagine, as long as you don't lose sight of the main goal: creating a uniform aluminum envelope around the device without it touching the device directly. The images below show two variants. The first has a second box inside (essentially pieces of cardboard), while the outer wooden box is covered in aluminum foil. The second eliminates the extra cardboard and lets the shoebox itself act as the insulator between the phone and the outer aluminum layer.
The Importance of a Good Seal
One of the most important details is that in both cases we see overlapping aluminum at the edges, so the lid closes hermetically (including friction, simple contact isn't enough) and there's continuity across the material. So what else can you use? Results vary wildly from one design to another, but we've seen examples based on metal trash cans (with a plastic can inside) and ammunition boxes. Now, seal quality is critical. The most expensive Faraday bags have a closure system that forces you to roll the top of the bag two or three times. Ideally, you'd completely seal the box with aluminum tape (as Dr. Arthur Bradley teaches in the video below), but presumably you want to take the device out with some frequency.
Why DIY Faraday Boxes Often Fail
That leads us to the huge number of cases where homemade Faraday boxes seem to fail, with radios and phones still working inside. What's the problem? Basically, we're dealing with devices that require very little energy to function, and any unexpected leak in the box causes direct failure. In short: don't stop trying. Change materials or the overall design if needed. If results aren't positive, there's always the nuclear option: get a phone with a removable battery and take it out when you're not using it. Even the most robust spying or telemetry system can't escape the absence of a power source. At the end of the day, when it comes to computer security, paranoia works.
