man-in-the-middle

18 Articles

Spoofed Serial Number Unlocks Cricut Machine

August 21, 2026 by 48 Comments

[xssfox] recently found a Cricut Maker in an e-waste disposal. A quick scan over the device indicated it was in moderately good condition, with merely some perished rollers to contend with. The device was salvaged, with the awareness that Cricut is plenty good at disabling and locking down machines when it wishes. However, those measures didn’t stop [xssfox] from bringing it back to life.

The suspicion was that the machine had been locked out after the original owner received a warranty replacement or similar. Whatever the reason, the rollers would have to be repaired and the machine unlocked if it were ever to cut (Cricut?) again. Hooking the machine up to Cricut software showed that it was “deactivated”, so there was work to do.

The rollers were not a difficult replacement, but the hacking would take a little work. Examining the motherboard didn’t reveal any obvious EEPROMs, and the microcontroller was not one [xssfox] had the debugger to work with. Thus, attention turned to intercepting communications between the machine and the host PC over USB. This revealed the machine sending its serial number to the Cricut PC software in plain text with no checksums or encryption at all. Unlocking the machine was as easy as installing an RP2040 in between the Cricut Maker and the host PC. It was programmed to relay packets between the two and spoof the serial number in the process.

[xssfox] suspects a software-only solution may be possible, too, though hasn’t implemented one yet. We’ve featured her work before, too, like her efforts to spoof emergency traffic light preemption signals.

Man-in-the-Middle PCB Unlocks HP Ink Cartridges

September 28, 2024 by 150 Comments

It’s a well-known secret that inkjet ink is being kept at artificially high prices, which is why many opt to forego ‘genuine’ manufacturer cartridges and get third-party ones instead. Many of these third-party ones are so-called re-manufactured ones, where a third-party refills an empty OEM cartridge. This is increasingly being done due to digital rights management (DRM) reasons, with tracking chips added to each cartridge. These chip prohibit e.g. the manual refilling of empty cartridges with a syringe, but with the right tweak or attack can be bypassed, with [Jay Summet] showing off an interesting HP cartridge DRM bypass using a physical man-in-the-middle-attack.

This bypass takes the form of a flex PCB with contacts on both sides which align with those on the cartridge and those of the printer. What looks like a single IC in a QFN package is located on the cartridge side, with space for it created inside an apparently milled indentation in the cartridge’s plastic. This allows is to fit flush between the cartridge and HP inkjet printer, intercepting traffic and presumably telling the printer some sweet lies so that you can go on with that print job rather than dash out to the store to get some more overpriced Genuine HP-approved cartridges.

Not that HP isn’t aware or not ticked off about this, mind. Recently they threatened to brick HP printers that use third-party cartridges if detected, amidst vague handwaving about ‘hackers’ and ‘viruses’ and ‘protecting the users’ with their Dynamic Security DRM system. As the many lawsuits regarding this DRM system trickle their way through the legal system, it might be worth it to keep a monochrome laser printer standing by just in case the (HP) inkjet throws another vague error when all you want is to just print a text document.

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Going To Extremes To Block YouTube Ads

August 26, 2023 by 109 Comments

Many users of YouTube feel that the quality of the service has been decreasing in recent years — the platform offers up bizarre recommendations, fails to provide relevant search results, and continues to shove an increasing amount of ads into the videos themselves. For shareholders of Google’s parent company, though, this is a feature and not a bug; and since shareholder opinion is valued much more highly than user opinion, the user experience will likely continue to decline. But if you’re willing to put a bit of effort in you can stop a large chunk of YouTube ads from making it to your own computers and smartphones.

[Eric] is setting up this adblocking system on his entire network, so running something like Pi-hole on a single-board computer wouldn’t have the performance needed. Instead, he’s installing the pfSense router software on a mini PC. To start, [Eric] sets up a pretty effective generic adblocker in pfSense to replace his Pi-hole, which does an excellent job, but YouTube is a different beast when it comes to serving ads especially on Android and iOS apps. One initial attempt to at least reduce ads was to subtly send YouTube traffic through a VPN to a country with fewer ads, in this case Italy, but this solution didn’t pan out long-term.

A few other false starts later, all of which are documented in detail by [Eric] for those following along, and eventually he settled on a solution which is effectively a man-in-the-middle attack between any device on his network and the Google ad servers. His router is still not powerful enough to decode this information on the fly but his trick to get around that is to effectively corrupt the incoming advertising data with a few bad bytes so they aren’t able to be displayed on any devices on the network. It’s an effective and unique solution, and one that Google hopefully won’t be able to patch anytime soon. There are some other ways to improve the miserable stock YouTube experience that we have seen as well, like bringing back the dislike button.

Thanks to [Jack] for the tip!

Speaker Snitch Tattles On Privacy Leaks

December 9, 2020 by 33 Comments

A wise senator once noted that democracy dies with thunderous applause. Similarly, it’s also how privacy dies, as we invite more and more smart devices willingly into our homes that are built by companies that don’t tend to have our best interests in mind. If you’re not willing to toss all of these admittedly useful devices out of the house but still want to keep an eye on what they’re doing, though, [Nick Bild] has a handy project that lets you keep an eye on them when they try to access the network.

The device is built on a Raspberry Pi that acts as a middle man for these devices on his home network. Any traffic they attempt to send gets sent through the Pi which sniffs the traffic via a Python script and is able to detect when they are accessing their cloud services. From there, the Pi sends an alert to an IoT Arduino connected to an LED which illuminates during the time in which the smart devices are active.

The build is an interesting one because many smart devices are known to listen in to day-to-day conversation even without speaking the code phrase (i.e. “Hey Google” etc.) and this is a great way to have some peace-of-mind that a device is inactive at any particular moment. However, it’s not a foolproof way of guaranteeing privacy, as plenty of devices might be accessing other services, and still other devices have  even been known to ship with hidden hardware.

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Inside A CAN Bus Mileage Manipulator

March 13, 2020 by 29 Comments

In the days of carburetors and leaf spring suspensions, odometer fraud was pretty simple to do just by disconnecting the cable or even winding the odometer backwards. With the OBD standard and the prevalence of electronics in cars, promises were made by marketing teams that this risk had all but been eliminated. In reality, however, the manipulation of CAN bus makes odometer fraud just as easy, and [Andras] is here to show us exactly how easy with a teardown of a few cheap CAN bus adapters.

We featured another project that was a hardware teardown of one of these devices, but [Andras] takes this a step further by probing into the code running on the microcontroller. One would imagine that basic measures would have been taken by the attackers to obscure code or at least disable debugging modes, but on this one no such effort was made. [Andras] was able to dump the firmware from both of his test devices and start analyzing them.

Analyzing the codes showed identical firmware running on both devices, which made his job half as hard. It looked like the code was executing a type of man-in-the-middle attack on the CAN bus which allowed it to insert the bogus mileage reading. There’s a lot of interesting information in [Andras]’s writeup though, so if you’re interested in CAN bus or attacks like this, it’s definitely worth a read.

Samy Kamkar: Reverse Engineering For A Secure Future

January 2, 2018 by 15 Comments

Show of hands: how many of you have parked your car in the driveway, walked up to your house, and pressed your car’s key fob button thinking it would open the front door? We’ve probably all done it and felt a little dopey as a result, but when you think about it, it would be tremendously convenient, especially with grocery bags dangling off each arm and the mail clenched between your teeth. After all, we’re living in the future —  shouldn’t your house be smart enough to know when you’re home?

Reverse engineer par excellence Samy Kamkar might think so, but given his recent experiences with cars smart enough to know when you’re standing outside them, he’d probably have some reservations. Samy dropped by the 2017 Hackaday Superconference in November to discuss the finer points of exploiting security flaws in passive car entry systems, and also sat down with our own Elliot Williams after his talk for a one-on-one interview. Samy has some interesting insights on vehicle cybersecurity, but the practical knowledge he’s gained while exploring the limits of these systems teach some powerful lessons about being a real-world reverse engineer.

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Hacking 2.4GHz Radio Control

September 20, 2015 by 6 Comments

Many modern radio control (RC) systems use frequency hopping to prevent interference. Unfortunately, hopping all over the 2.4GHz band can interfere with video or WiFi using the same frequency band. [Befinitiv] was trying to solve this problem when he realized that most of the systems used a TI CC2500 chip and a microcontroller. The microcontroller commands the chip via SPI and controls the frequency by writing into a frequency register.

Updating the microcontroller firmware was impractical. The firmware is encrypted, for one thing. In addition, the change would have to be reinserted on any future updates and repeated for every RC vendor. So [Befinitiv] took a different approach. He did a classic man in the middle attack by inserting an CPLD in between the controller and the CC2500.

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