An IMSI catcher is an illicit mobile phone base station designed to intercept the traffic from nearby mobile phones by persuading them to connect to it rather than the real phone company tower. The IMSI in the name stands for International Mobile Subscriber Identity, a unique global identifier that all mobile phones have. IMSI catchers are typically used by government agencies to detect and track people at particular locations, and are thus the subject of some controversy.
As is so often the case when a piece of surveillance technology is used in a controversial manner there is a counter-effort against it. The IMSI catchers have spawned the subject of this post, an IMSI catcher detector app for Android. It’s a work-in-progress at the moment with code posted in its GitHub repository, but it is still an interesting look into this rather shadowy world.
How them you might ask, does this app hope to detect the fake base stations? In the first case, it will check the identity of the station it is connected to against a database of known cell towers. Then it will try to identify any unusual behaviour from the base station by analysing its traffic and signal strength. Finally it will endeavour to spot anomalies in the implementation of the cell phone protocols that might differentiate the fake from the real tower.
They have made some progress but stress that the app is in alpha stage at the moment, and needs a lot more work. They’re thus inviting Android developers to join the project. Still, working on projects is what the Hackaday Prize is all about.
Think not of what you see, but what it took to produce what you see
Randomness is all around you…or so you think. Consider the various shapes of the morning clouds, the jagged points of Colorado’s Rocky Mountains, the twists and turns of England’s coastline and the forks of a lightning bolt streaking through a dark, stormy sky. Such irregularity is commonplace throughout our natural world. One can also find similar irregular structures in biology. The branch-like structures in your lungs called Bronchi, for instance, fork out in irregular patterns that eerily mirror the way rivers bifurcate into smaller streams. It turns out that these irregular structures are not as irregular and random as one might think. They’re self-similar, meaning the overall structure remains the same as you zoom in or out.
The mathematics that describes these irregular shapes and patterns would not be fully understood until the 1970s with the advent of the computer. In 1982, a renegade mathematician by the name of Benoit Mandelbrot published a book entitled “The Fractal Geometry of Nature”. It was a revision of his previous work, “Fractals: Form, Chance and Dimension” which was published a few years before. Today, they are regarded as one of the ten most influential scientific essays of the 20th century.
Mandelbrot coined the term “Fractal,” which is derived from the Latin word fractus, which means irregular or broken. He called himself a “fractalist,” and often referred to his work as “the study of roughness.” In this article, we’re going to describe what fractals are and explore areas where fractals are used in modern technology, while saving the more technical aspects for a later article.
The idea is that phones are increasingly complex and potentially vulnerable to all kinds of digital surveillance. Even airplane mode is insufficient for knowing that your phone isn’t somehow transmitting information. The paper looks at the various radios on the iPhone, going so far as opening up the device and reading signals at each of the chips for cell, WiFi, Bluetooth, GPS, and NFC to determine whether the chip itself is doing anything, regardless of what the screen says. This introspection can then be used to be confident that the phone is not communicating when it shouldn’t be.
The paper goes on to propose a device that they will prototype in the coming year which uses an FPC that goes into the phone through the SIM card port. It would contain a battery, display, buttons, multiple SIM cards, and an FPGA to monitor the various buses and chips and report on activity.
Significant hacking of an iPhone will still be required, but the idea is to increase transparency and be certain that your device is only doing what you want it to.
The launch of Pokemon Go has unleashed the franchise upon the world once again but this time it’s encouraging users to get active and socialize in the great outdoors. To show off their dedication to the cause, [Npoole] 3D printed a Pokédex external battery and case to combat the game’s already legendary drain on their Galaxy S4’s resources.
Mimicking the first-generation Kanto design, [Npoole] 3D printed it in red ABS and added a small circuit with a red, yellow and green LED to complete the effect. Inside, a 18650 lithium cell provides the much-needed backup power via a micro B plug and is boosted to 5V with a LiPo charger/booster board. Despite a switch on the circuit, the battery slowly drains so that’s something to be corrected in a future version.
As you can see, there is still some room left over in the external bat–I mean–Pokédex, and [Npoole] intends to add another battery and a cooling fan to further improve the design. The result is a little bulky, but for new and diehard fans alike, a working Pokédex definitely worth it.
While building a robot (nearly) from scratch isn’t easy, it needn’t be a lengthy process. Is it possible to build a bot in a single day? With some musical motivation (a 10 hour loop of the A-Team theme song), [Tyler Bletsch] answers with a resounding ‘yes’ in the shape of his little yellow robot that he built for a local robotics competition.
Designing and fabricating on the fly, [Bletsch] used Sketchup to design the chassis, and OpenSCAD to model the wheels while the former was being 3D printed. Anticipating some structural weakness, he designed another version that could bolt to wood if the original failed, but the addition of some metal support rods provided enough stability. Mouse pad material gave the wheels ample traction. An Arduino with the L298 control module receives input via an HC-06 Bluetooth board. Eight AA batteries provide 12V of power to two Nextrox mini 12V motors with an integrated voltmeter to measure battery life.
Sometimes you start building, and the project evolves. Layers upon layers of functionality accrue, accrete, and otherwise just pile up. Or at least we’re guessing that’s what happened with [Varun Kumar]’s sweet “Surveillance Car Controlled by DTMF“.
In case you haven’t ever dug into not-so-ancient telephony, Dual-tone, multi-frequency signalling is what made old touch-tone phones work. DTMF, as you’d guess, encodes data in audio by playing two pitches at once. Eight tones are mapped to sixteen numbers by using a matrix that looks not coincidentally like the old phone keypad (but with an extra column). One pitch corresponds to a column, and one to a row. Figure out which tones are playing, and you’ve decoded the signal.
Anyway, you can get DTMF decoder chips for pennies on eBay, and they make a great remote-control interface for a simple robot, which is presumably how [Varun] got started. And then he decided that he needed a cell phone on the robot to send back video over WiFi, and realized that he could also use the phone as a remote controller. So he downloaded a DTMF-tone-generator app to the phone, which he then controls over VNC. Details on GitHub.
[Mr. Volt] mentions that some of the commenters on his videos believed that he shouldn’t be making large, retro computer themed communicator watches. He believes they are wrong, naturally we are compelled to agree with him.
In his latest build he has produced a rather well-built and large cell-phone watch. After the untimely death of an Apple II cellphone watch, he decided to up his game and make one that could take more of a beating. The case is 3D printed, which is hard to believe given the good finish. He must have spent a long time sanding the prints. Some wood veneer for looks and aluminum panels for strength complete the assembly.
The electronics are a Teensy and a GSM module. It looks like he places calls by calling the operator since the wrist communicator only has four inputs: a red button, a blue button, and a momentary switch rotary encoder.
The communicator appears to work really smoothly, and it would certainly draw attention to him were he to wear it anywhere other than the Wasteland. Video after the break.