Over-molding Wires With Hot Glue And 3D Printed Molds

August 2, 2024 by Dan Maloney 48 Comments

We’ve said it before and we’ll say it again: water always finds a way in. That’s particularly problematic for things like wire splices in damp environments, something that no amount of electrical tape is going to help. Heat shrink tubing might be your friend here, but for an electrically isolated and mechanically supported repair, you may want to give over-molding with a hot glue gun a try.

The inspiration for [Print Practical]’s foray into over-molding came from a video that’s making the rounds showing a commercially available tool for protecting spliced wires in the automotive repair trade. It consists of a machined aluminum mold that the spliced wires fit into and a more-or-less stock hot glue gun, which fills the mold with melted plastic. [Print Practical] thought it just might be possible to 3D print custom molds at home and do it himself.

His first attempt didn’t go so well. As it turns out, hot glue likes to stick to things — who knew? — including the PETG mold he designed. Trying to pry apart the mold after injection was a chore, and even once he got inside it was clear the glue much preferred to stay in the mold. Round two went much better — same wire, same mold, but now with a thin layer of vegetable oil to act as a release agent. That worked like a charm, with the over-mold standing up to a saltwater bath with no signs of leaking. [Print Practical] also repaired an iPhone cable that has seen better days, providing much-needed mechanical support for a badly frayed section.

This looks like a fantastic idea to file away for the future, and one that’s worth experimenting with. Other filament types might make a mold better able to stand up to the hot glue, and materials other than the ethylene-vinyl acetate copolymer found in most hot glue sticks might be explored. TPU over-molds, anyone? Or perhaps you can use a printer as an injector rather than the glue gun.

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Injecting Bugs With An Electric Flyswatter

March 15, 2021 by Stephen Ogier 9 Comments

Hardware fault injection uses electrical manipulation of a digital circuit to intentionally introduce errors, which can be used to cause processors to behave in unpredictable ways. This unintentional behavior can be used to test for reliability, or it can be used for more nefarious purposes such as accessing code and data that was intended to be inaccessible. There are a few ways to accomplish this, and electromagnetic fault injection uses a localized electromagnetic pulse to flip bits inside a processor. The pulse induces a voltage in the processor’s circuits, causing bits to flip and often leading to unintentional behavior. The hardware to do this is very specialized, but [Pedro Javier] managed to hack a $4 electric flyswatter into an electromagnetic fault injection tool. (Page may be dead, try the Internet Archive version.)

[Pedro] accomplishes this by turning an electric flyswatter into a spark-gap triggered EMP generator. He removes the business end of the flyswatter and replaces it with a hand-wound inductor in series with a small spark gap. Pressing the power button on the modified flyswatter charges up the output capacitor until the developed voltage is enough to ionize the air in the spark gap, at which point the capacitor discharges through the inductor. The size of the spark gap determines the charge that is built up—a larger gap results in a larger charge, which produces a larger pulse, which induces a larger voltage in the chip.

[Pedro] demonstrates how this can be used to produce arithmetic glitches and even induce an Arduino to dump its memory. Others have used electromagnetic fault injection to corrupt SRAM, and intentionally glitching the power supply pins can also be used to access otherwise protected data.

This USB Drive Will Self-Destruct After Ruining Your Computer

January 19, 2018 by Dan Maloney 35 Comments

Who would have thought that you could light up pyrotechnics on USB power? This USB keystroke injector that blows up after it’s used proves the concept.

Fully aware that this is one of those “just because you can doesn’t mean you should” projects, [MG] takes pains to point out that his danger dongle is just for dramatic effect, like a prop for a movie or the stage. In fact, he purposely withholds details on the pyrotechnics and concentrates on the keystroke injection aspect, potentially nasty enough by itself, as well as the dongle’s universal payload launching features. We’re a little bummed, because the confetti explosion (spoiler!) was pretty neat.

The device is just an ATtiny85 and a few passives stuffed into an old USB drive shell, along with a MOSFET to trigger the payload. If you eschew the explosives, the payload could be anything that will fit in the case. [MG] suggests that if you want to prank someone, an obnoxious siren might be a better way to teach your mark a lesson about plugging in strange USB drives.

While this isn’t the most dangerous thing you can do with a USB port, it could be right up there with that rash of USB killer dongles from a year or so ago. All of these devices are fun “what ifs”, but using them on anything but your own computers is not cool and possibly dangerous. Watching the smoke pour out of a USB socket definitely drives home the point that you shouldn’t plug in that thumbdrive that you found in the bathroom at work, though.

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Injecting Code Into Mouse Firmware Should Be Your Next Hack

July 29, 2017 by Mike Szczys 22 Comments

Here’s a DEF CON talk that uses tools you likely have and it should be your next hacking adventure. In their Saturday morning talk [Mark Williams] and [Rob Stanely] walked through the process of adding their own custom code to a gaming mouse. The process is a crash course in altering a stock firmware binary while still retaining the original functionality.

The jumping off point for their work is the esports industry. The scope of esporting events has blown up in recent years. The International 2016 tournament drew 17,000 attendees with 5 million watching online. The prize pool of $20 million ($19 million of that crowdfunded through in-game purchases) is a big incentive to gain a competitive edge to win. Contestants are allowed to bring their own peripherals which begs the questions: can you alter a stock gaming mouse to do interesting things?

The steelseries Sensei mouse was selected for the hack because it has an overpowered mircocontroller: the STM32F103CB. With 128 KB of flash the researchers guessed there would be enough extra room for them to add code. STM32 chips are programmed over ST-Link, which is available very inexpensively through the ST Discovery boards. They chose the STM32F4DISCOVERY which runs around $20.

Perhaps the biggest leap in this project is that the firmware wasn’t read-protected. Once the data, clock, and ground pads on the underside of the board were connected to the Discovery board the firmware was easy to dump and the real fun began.

They first looked through the binary for a large block of zero values signifying unused space in flash. The injected firmware is designed to enumerate as a USB keyboard, open Notepad, then type out, save, and execute a PowerShell script before throwing back to the stock firmware (ensuring the mouse would still function as a mouse). Basically, this builds a USB Rubber Ducky into stock mouse firmware.

There are a few useful skills that make taking on this project a worthwhile learning experience. To compile your custom code correctly you need to choose the correct offset address for where it will end up once pasted into the firmware binary. The vector table of the original code must be rewritten to jump to the injected code first, and it will need to jump back to the mouse execution once it has run. The program flow on the left shows this. Both of these jumps require the program counter and registers to be saved and restored. The ARM stack is subtractive and the address will need to be updated to work with the added code.

The talk ended with a live demo that worked like a charm. You can check out the code in the MDHomeBrew repo. In this case the PowerShell script adds keyboard shortcuts for DOOM cheats. But like we said before, the experience of getting under the hood with the firmware binary is where the value will be for most people. With this success under your belt you can take on more difficult challenges like [Sprite_TM’s] gaming keyboard hack where the firmware couldn’t easily be dumped and an update binary was quite obsfucated.

MalDuino — Open Source BadUSB

January 24, 2017 by Pedro Umbelino 28 Comments

MalDuino is an Arduino-powered USB device which emulates a keyboard and has keystroke injection capabilities. It’s still in crowdfunding stage, but has already been fully backed, so we anticipate full production soon. In essence, it implements BadUSB attacks much like the widely known, having appeared on Mr. Robot, USB Rubber Ducky.

It’s like an advanced version of HID tricks to drop malicious files which we previously reported. Once plugged in, MalDuino acts as a keyboard, executing previous configured key sequences at very fast speeds. This is mostly used by IT security professionals to hack into local computers, just by plugging in the unsuspicious USB ‘Pen’.

[Seytonic], the maker of MalDuino, says its objective is it to be a cheaper, fully open source alternative with the big advantage that it can be programmed straight from the Arduino IDE. It’s based on ATmega32u4 like the Arduino Leonardo and will come in two flavors, Lite and Elite. The Lite is quite small and it will fit into almost any generic USB case. There is a single switch used to enable/disable the device for programming.

The Elite version is where it gets exciting. In addition to the MicroSD slot that will be used to store scripts, there is an onboard set of dip switches that can be used to select the script to run. Since the whole platform is open sourced and based on Arduino, the MicroSD slot and dip switches are entirely modular, nothing is hardcoded, you can use them for whatever you want. The most skilled wielders of BadUSB attacks have shown feats like setting up a fake wired network connection that allows all web traffic to be siphoned off to an outside server. This should be possible with the microcontroller used here although not native to the MalDuino’s default firmware.

For most users, typical feature hacks might include repurposing the dip switches to modify the settings for a particular script. Instead of storing just scripts on the MicroSD card you could store word lists on it for use in password cracking. It will be interesting to see what people will come up with and the scripts they create since there is a lot of space to tinker and enhanced it. That’s the greatness of open source.

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DEFCON 22: Hack All The Things

August 9, 2014 by Mike Szczys 21 Comments

This morning I went to a fantastic talk called Hack All the Things. It was presented by GTVHacker. If you don’t recognize the name, this is the group that hacked the GoogleTV. They haven’t stopped hacking since that success, and this talk is all about 20+ devices that they’ve recently pwned and are making the info public (that link still had oath when I checked but should soon be public).

The attacks they presented come in three flavors: UART, eMMC, and command injection bugs. I’m going to add the break now, but I’ll give a rundown of most of the device exploits they showed off. I found all amusing, and often comical.

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More 555 Projects To Enjoy

February 7, 2011 by James Munns 9 Comments

We love all of the projects that are coming out for the 555 design contest, so we thought we would share a couple more that have caught our collective eye. Have a 555 project of your own? Be sure to share it with us, and keep an eye out for the contest submission dates. Read on for a few of our project picks.

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