A Simple, DIY GPS Tracker

Today, there are dozens of off-the-shelf solutions for a GPS tracking device. Most of them use GSM, some of them use satellites, and all of them are astonishingly inexpensive. If you want to track a car, dog, or your luggage, you’ve never had more options.

[Emilio] wanted to track his own car, and the original solution for this was a smartphone. This smartphone was also a good choice, as it’s a programmable GPS device connected to a cell network, but there had to be a simpler solution. It came in the form of an eight euro GPS module and a three euro GSM module (Google Translatrix right here). The rest of the hardware is an ATMega48V [Emilio] had sitting around and a 2500 mAh lithium cell. It’s a cellular tracker make out of eleven euro’s worth of hardware and some junk in a drawer.

There are only a few caveats to this hardware. First, the ATmega48V only has one UART. This is connected to the GPS module at 9600, 8N1. The connection to the GSM M-590 module is only 2400 bps, and slow enough for a bitbanged UART. This hardware is soldered to a piece of perfboard, thus ending the hardware part of this build.

The software is a little more complex, but not by very much. The GPS part of the firmware records the current latitude and longitude. If the GSM module receives a call, it replies with an SMS of the current GPS coordinates and a few GPS coordinates seen earlier. Of course, a pre-paid SIM is required for this build, but those are cheap enough.

Not even ten years ago, a simple, DIY GPS tracker would have cost a small fortune. Now that we have cheap GPS modules, GSM modules, and more magical electronics from the East, builds like this are easy and cheap. What a magical time to be alive.

Cheap Modules Upgrade Home Security System

[gw0udm] had an ancient monitored alarm system fitted to their home, and decided it was time to upgrade to something a little more modern. They chose a system from Texecom, but when it came time to hook it up to their computer, they were alarmed at the costs – £40 for what amounted to a USB-to-Serial cable! There were other overpriced modules too. But [gw0udm] wanted to upgrade, so it was time to hack the system.

The first step was grabbing a £4 USB-to-Serial board and wiring it up – a simple job for the skilled hacker.  As we always say – everything speaks serial. [gw0udm] then set their sights higher – they wanted the Ethernet interface but weren’t about to cough up the coin. After some research, it was determined that a Raspberry Pi could be used with a utility called ser2net with the existing serial interface to do pretty much the same job. It was a simple matter of figuring out the parity and messaging format to get things up and running.

From there, the project moves on to tackling the creation of a GSM module for monitoring in the absence of a local network, and on flashing the firmware of the system itself. It’s great to see a project continually grow and expand the functionality of a product over time.

We see a lot of security systems here at Hackaday – high prices and proprietary hardware tend to inspire the hacker spirit. Check out this reverse engineering of an obsolete 1980s system, resplendent with Eurostile font.

GSM Sniffing on a Budget with Multi-RTL

If you want to eavesdrop on GSM phone conversations or data, it pays to have deep pockets, because you’re going to need to listen to a wide frequency range. Or, you can just use two cheap RTL-SDR units and some clever syncing software. [Piotr Krysik] presented his work on budget GSM hacking at Camp++ in August 2016, and the video of the presentation just came online now (embedded below). The punchline is a method of listening to both the uplink and downlink channels for a pittance.

[Piotr] knows his GSM phone tech, studying it by day and hacking on a GnuRadio GSM decoder by night. His presentation bears this out, and is a great overview of GSM hacking from 2007 to the present. The impetus for Multi-RTL comes out of this work as well. Although it was possible to hack into a cheap phone or use a single RTL-SDR to receive GSM signals, eavesdropping on both the uplink and downlink channels was still out of reach, because it required more bandwidth than the cheap RTL-SDR had. More like the bandwidth of two cheap RTL-SDR modules.

Getting two RTL-SDR modules to operate in phase is as easy as desoldering a crystal from one and slaving it to the other. Aligning the two absolutely in time required a very sweet hack. It turns out that the absolute timing is retained after a frequency switch, so both RTL-SDRs switch to the same channel, lock together on a single signal, and then switch back off, one to the uplink frequency and the other to the downlink. Multi-RTL is a GnuRadio source that takes care of this for you. Bam! Hundreds or thousands of dollar’s worth of gear replaced by commodity hardware you can buy anywhere for less than a fancy dinner. That’s a great hack, and a great presentation.
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Building Beautiful Cell Phones Out Of FR4

Over on Hackaday.io, [bobricius] took this technology and designed something great. It’s a GSM cell phone with a case made out of FR4. It’s beautiful, and if you’re ever in need of a beautifully crafted burner phone, this is the one to build.

The components, libraries, and toolchains to build a cellphone from scratch have been around for a very long time. Several years ago, the MIT Media Lab prototyped a very simple cellphone on a single piece of FR4. It made calls, but not much else. It was ugly, but it worked. [Bobricius] took the idea and ran with it.

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Barely-There GSM GPS Tracker

What’s the most un-intrusive GPS you’ve ever seen? How about for a bike? Redditor [Fyodel] has built a Teensy-based GPS/GSM tracker that slides into your bike’s handlebars and really is out of sight.

The tracker operates on T-Mobile’s 2G service band — which will enable the device to work until about 2020 — since AT/T is phasing out their service come January. Since each positioning message averages 60 bytes, an IoT data plan is sufficient for moderate usage, with plans to switch over to a narrow-band LTE service when it becomes more affordable. [Fyodel] admits that battery life isn’t ideal at the moment, but plans to make it more efficient by using a motion sensor to ensure it’s only on when it needs to be.

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Rotary Cell Phone: Blast from a Past that Never Was

The 1970s called and they want their rotary dial cell phone back.

Looking for all the world like something assembled from the Radio Shack parts department – remember when Radio Shack sold parts? – [Mr_Volt]’s build is a celebration of the look and feel of a hobbyist build from way back when. Looking a little like a homebrew DynaTAC 8000X, the brushed aluminum and 3D-printed ABS case sports an unusual front panel feature – a working rotary dial. Smaller than even the Trimline phone’s rotating finger stop dial and best operated with a stylus, the dial translates rotary action to DTMF tones for the Feather FONA board inside. Far from a one-trick pony, the phone sports memory dialing, SMS messaging, and even an FM receiver. But most impressive and mysterious is the dial mechanism, visible through a window in the wood-grain back. Did [Mr_Volt] fabricate those gears and the governor? We’d love to hear the backstory on that.

This isn’t the first rotary cell phone hybrid we’ve featured, of course. There was this GSM addition to an old rotary phone and this cell phone that lets you slam the receiver down. But for our money a rotary dial cell phone built from the ground up wins the retro cool prize of the bunch.

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How To Detect And Find Rogue Cell Towers

Software defined radios are getting better and better all the time. The balaclava-wearing hackers know it, too. From what we saw at HOPE in New York a few weeks ago, we’re just months away from being able to put a femtocell in a desktop computer for under $3,000. In less than a year, evil, bad hackers could be tapping into your cell phone or reading your text message from the comfort of a van parked across the street. You should be scared, even though police departments everywhere and every government agency already has this capability.

These rogue cell sites have various capabilities, from being able to track an individual phone, gather metadata about who you have been calling and for how long, to much more invasive surveillance such as intercepting SMS messages and what websites you’re visiting on your phone. The EFF calls them cell-site simulators, and they’re an incredible violation of privacy. While there was most certinaly several of these devices at DEF CON, I only saw one in a hotel room (you catchin’ what I’m throwin here?).

No matter where the threat comes from, rogue cell towers still exist. Simply knowing they exist isn’t helpful – a proper defence against governments or balaclava wearing hackers requires some sort of detection system.. For the last few months [Eric Escobar] has been working on a simple device that allows anyone to detect when one of these Stingrays or IMSI catchers turns on. With several of these devices connected together, he can even tell where these rogue cell towers are.

A Stingray / cell site simulator detector
A Stingray / cell site simulator detector

Stingrays, IMSI catchers, cell site simulators, and real, legitimate cell towers all broadcast beacons containing information. This information includes the radio channel number, country code, network code, an ID number unique to a large area, and the transmit power. To make detecting rogue cell sites harder, some of this information may change; the transmit power may be reduced if a tech is working on the site, for instance.

To build his rogue-cell-site detector, [Eric] is logging this information to a device consisting of a Raspberry Pi, SIM900 GSM module, an Adafruit GPS module, and a TV-tuner Software Defined Radio dongle. Data received from a cell site is logged to a database along with GPS coordinates. After driving around the neighborhood with his rogue-cell-site detector sitting on his dashboard, [Eric] had a ton of data that included latitude, longitude, received power from a cell tower, and the data from the cell tower. This data was thrown at QGIS, an open source Geographic Information System package, revealing a heatmap with the probable locations of cell towers highlighted in red.

This device really isn’t a tool to detect only rogue cell towers – it finds all cell towers. Differentiating between a rogue and legitimate tower still takes a bit of work. If the heatmap shows a cell site on a fenced-off parcel of land with a big tower, it’s a pretty good bet that cell tower is legit. If, however, the heatmap shows a cell tower showing up on the corner of your street for only a week, that might be cause for alarm.

Future work on this cell site simulator detector will be focused on making it slightly more automatic – three or four of these devices sprinkled around your neighborhood would easily allow you to detect and locate any new cell phone tower. [Eric] might also tackle triangulation of cell sites with an RF-blocking dome with a slit in it revolving around the GSM900 antenna.