Common Embedded Systems Hardware Attacks

Welcome dear networkseclearners to this new exciting tutorial in which we are going to explore some common embedded systems hardware attacks. Have you ever heard about embedded systems? I am sure you have because embedded systems are everywhere nowadays from things you wear like smartwatch, pacemakers, smartphones or any IoTs devices to things that are more sophiscated like cars, industrial robots and medical devices. As you can see, these systems are everywhere and very important in our daily life. Now, guess what can be the consequences if a critical embedded system in a car is attacked while the user drives. It can be very dangerous, right? 😉 I talked more about this matter in another article that can be found here : Introduction to Automotive Cybersecurity

This tutorial will be focused on the attacks on the Hardware of embedded systems. As you might already know, embedded systems are made of Hardware components like microcontroller or systems on Chip and Software. When we talk about hardware attacks, people usually think of someone opening a device and messing with its hardware components. This is partly true because Hardware attacks often do start by targeting physical components like the JTAG debug port. But guess what? Sometimes, attackers use software tricks to mess with the hardware like bypassing a password check or glitching the system into making the wrong decisions. Cool and scary, right? 🤔

In this article and in the next section, we will explore some common attacks against embedded systems Hardware based on real techniques used by hackers and security researchers. This tutorial as always to allow everybody from layman to expertise levels to understand. But, it is still can be hard for people who are not familiar with embedded systems to understand some concepts. So, I would strongly recommend to ask any questions you may have in the comment section. Of course, don’t hesitate to correct and make suggestions for improvement of this article. Now, let’s get started!!🙏

1. PCB Level Attacks

Do you know what PCB stands for? If not, PCB stands for Printed Circuit Board and is the board on which reside all electronics components like resistors, microcontrollers, memory chips etc and their connection. The Printed Circuit Board is like the heart and nervous system of any device. And for an attacker, it is often the first and juiciest target and that is because the layout of the board gives away some secrets : test points, debug ports, resistors.

Some smart chips use “straps” which are tiny 0-ohm resistors to set their boot behavior. If we want to enable debug mode or skip signature checks on firmware, we can just add or remove these resistors.

And it even goes furthter with flash chips the place where firmware lives because if they are not encrypted or properly locked, attackers can read them with special tools, extract code, clone them or even write their own modified version.

Sure, some devices try to defend themselves with tamper-resistant cases or “read-only” settings. But with enough skill (and a heat gun), attackers can still get in. That’s why good PCB design is not just about making the circuit work but it is also about hiding and protecting the stuff that matters for hackers.

2. Non Invasive Chip Attacks

You might wonder what weird expression is this because you might think we cannot attack chips without cracking, opening or damaging them. Well, it is possible to attack chips indeed without “touching” them.😉 In fact, Non invasive attacks are all about being clever getting information or access without leaving a scratch.😎

These attacks do not physically change the hardware but instead they rely on observing how a system behaves (like power usage or timing) or subtly causing it to glitch. For example, an attacker might send an electromagnetic pulse that tricks a device into skipping a password check.

While the techniques vary, the key idea is the same : stay outside, observe and manipulate. If you wanna know more about non invasive attacks, read the next sub sections where we are going to discuss the 2 most used non invasive chip attack techniques which are side-channel and fault injection attacks.

2.1 Side-Channel Attacks

In order to explain this in an easy way to understand, let’s use the following analogy : imagine you are watching someone enter a password on a keypad. You cannot see the screen but you notice how long they pause between keys or maybe you hear the beeps. Even without seeing the password, you might figure out what it is just by paying close attention. Did you follow me? sounds like magic, right? 😂 Well, that is the idea behind side-channel attacks.

Side-channel attacks are indeed sneaky techniques hackers use to steal secret information like passwords, cryptographic keys without touching the system’s code. Instead of breaking in, they observe how the device behaves through things like :

• How long it takes for the device to respond (timing)
• How much power it uses (power analysis)
• The tiny signals it sends out like electromagnetic waves (EM attacks)
• How memory behaves like in the RAM (Random Access Memory)

These small details can leak secret information like passwords or encryption keys even if the system looks perfectly secure on the outside. As we saw, side-channel attacks do not rely on software bugs but they exploit the physical behavior of devices. Modern microcontrollers usually embbed some hardware security modules which are protected against this kind of attacks.

2.2 Fault Injection

Similarly to side-channel attacks, let’s use another analogy to help you understand this kind of attacks more easily : Imagine your computer is like a very careful worker following instructions step by step. Now guess what happens if someone finds a way to confuse it on purpose just for a moment so it makes a mistake? Well, that is the basic idea of fault injection. Fault injection indeed consists in intentionally messing with a device so it makes an error like skipping a security check or flipping a bit in memory.

But the trick is not just making the error, the real danger is when hackers use that error to do something harmful like gaining access to secret parts of the system. When that happens, it becomes a fault attack. Here are some examples of some fault injections :

• Rowhammer :

This consists in hitting a part of memory so many times that nearby memory starts to change. It “hammers” memory until bits flip and then hackers can sneak into areas they should not be allowed to access.

• Overclocking the CPU :

Think of pushing the brain of your device (the CPU) to go faster than it is supposed to. That stress causes small errors like making it forget to check if a file is safe. If hackers time it just right, they can trick the system into running bad code.

To conclud on this topic of Fault Injection attack, we shall keep in mind that even without breaking the casing or cutting wires, attackers can cause little hiccups in how the system works and use those hiccups to their advantage. It is like exactly like slipping a word into someone’s ear while they are distracted just to make them sign the wrong paper. In modern microcontrollers, some mechanisms are implemented in order to detect and to react to these kind of attacks.

3. Chip-Invasive Attacks

In the previous chapter, we explored attacks on the chips which are not invasive which means we don’t physically attack the chip. As you might guess, sometimes, we need to be invasive in order to get some details at lower level like transistors level. But wait, what is transistor? for the readers who are not familiar with transistors, just think of transistors like switches which are controled by voltage. And chips are made of billions of transistors that’s why exploring their details can reveal some secrets on the chips. So, Unlike Non Invasive Chips attacks like side-channel or fault injection techniques that observe or disturb the device externally, chip-invasive methods go directly inside the chip to tamper with or study its inner workings. These attacks therefore operate at the microscopic level targeting tiny wires, gates and transistor and require expensive lab equipment, precision tools and expert-level knowledge. The chip-invasive attacks are among the most advanced forms of hardware hacking. Let’s discuss some of these attacks in the next sub sections.

3.1 Decapsulation, Depackaging and Rebonding

The process usually begins with decapsulation where acids like nitric or sulfuric acid are carefully applied to remove the protective packaging around the silicon chip. This creates a small opening that exposes the chip’s surfac allowing attackers to observe or interact with internal structures. Done properly, the chip remains operational even after partial exposure.

In more aggressive approaches, the entire chip is depackaged stripping away all packaging material. This exposes everything the die, bonding wires, and contact points. If the attacker wants to keep the chip functional, they must rebond it by reconnecting the delicate wires that link the silicon to the external pins of the package. While this process often results in a non-functional chip, it is still valuable for optical reverse engineering where attackers take high-resolution images of the chip’s layout to understand its design or extract secrets.

These techniques are typically out of reach for average hackers due to their complexity, cost, and the safety requirements involved. However, in high-stakes industries like aerospace, defense, or secure communications where intellectual property or cryptographic keys must be protected chip-invasive attacks represent a real and serious threat.

3.2 Microscopic Imaging and Reverse Engineering

Once the protective layers of a chip are removed, attackers can begin one of the most advanced forms of hardware reverse engineering. The first goal is to identify the major functional blocks on the chip like memory areas, interconnecting buses or ROM sections that hold the boot code. These blocks are often visible as distinct patterns or shapes on the silicon. However, the visible surface only shows the top metal layer. To fully understand the chip’s architecture, attackers use a process called delayering where each metal layer is polished away to reveal the one beneath it. This reveals the full stack of internal wiring and logic down to the transistors that make up the digital circuits. Most modern chips use a CMOS (Complementary Metal-Oxide-Semiconductor) structure with multiple layers of copper interconnects stacked above a base of transistors. High-resolution imaging of these layers allows experts to rebuild what is known as a netlist, a detailed map showing how all the logic gates are connected. Combined with a binary dump of the chip’s boot ROM, this reverse engineering can expose flaws in the hardware design or insecure code. It’s like peeling back the layers of a digital onion to reveal its secrets and when done right, it can tell you exactly how the chip works, right down to its last transistor.

3.3 Scanning Electron Microscope Imaging

When attackers want to go even deeper into the structure of a chip, they turn to tools like the Scanning Electron Microscope or SEM for short. Unlike regular optical microscopes which use light, an SEM uses a beam of electrons to scan the surface of the chip. This method can capture incredibly detailed images down to less than one nanometer which means you can actually see tiny things like individual transistors and wiring inside the silicon. These high-resolution images can then be used to recreate the chip’s circuitry often by building something called a netlist which is a detailed map of how all the logic components are connected. It’s like having X-ray vision for chips helping advanced attackers understand or even clone a design at the most fundamental level.

4. Debug Interface Abuse

Debug interfaces like JTAG (Joint Test Access Group) or SWD (Serial Wire Debug) are incredibly powerful and dangerous when left open. If they are not locked down properly, anyone with the right tool can connect and dump memory, change registers, or halt execution. It is shocking how many consumer and industrial devices ship with debug ports still active.😯

When engineers build a device, they need a way to check what is going on inside like a backstage pass to the CPU. That is what debugging and tracing interfaces are for. Think of them like special doors that let developers pause the system, peek at memory or test specific features. These doors usually come in the form of JTAG (Joint Test Access Group) or SWD (Serial Wire Debug) interfaces and if left unlocked, they are gold for hackers.

Sometimes, the manufacturer removes the header (the visible connector on the board) but the actual debug signals are still there just waiting for someone with soldering skills and a little curiosity. On more secure systems things like OTP fuses, hidden straps or cryptographic challenge-response systems are used to permanently disable or lock access. If the debug port is still active and you know where to connect, you basically get privileged access to the device. So, always make sure these VIP entrances are locked before shipping.

5. Flash Image Analysis

Many embedded devices have flash memory chips that store the firmware often located separately from the main microcontroller chip. If the device supports software updates, chances are you can find its firmware image online sometimes right from the manufacturer’s website or buried in update files.

Once you get your hands on a firmware image, the real fun begins thanks to tools like Binwalk that make it easier to dig into the image by identifying different parts such as executable code, data, filesystems and even digital signatures.

But hackers don’t stop there! They take things further with disassembly and decompiling which allows them to reverse-engineer the software and search for potential vulnerabilities. There is also growing interest in static analysis techniques such as concolic execution which try to analyze code paths without even running the firmware.

6. Microarchitectural Attacks

Modern CPUs are fast because of clever design tricks called microarchitectural optimizations. These include things like caching (keeping frequently used data close to the processor) and speculative execution (guessing which instructions will run next and starting them early). These features improve performance but they can also leak information. For example, if some data is already in the cache, the CPU can access it faster. By carefully measuring those access times, an attacker might figure out what data was recently used potentially even sensitive information like passwords or encryption keys.

One famous example is the Spectre attack. It tricks the CPU into running instructions speculatively (before it is sure they are needed) which affects the cache in subtle ways. Even though, the CPU later discards the results, those tiny side effects can be observed and used to recover secrets from memory. What makes these attacks dangerous is that they don’t break the software itself but they exploit how the hardware behaves. Traditional security tools like antivirus software won’t catch them and fixing the issue often requires both software patches and changes to how CPUs are built.

In short, microarchitectural attacks show us that performance boosts in hardware can sometimes come at the cost of security.

7. Fuzzing Embedded Devices

I hope you are still here with me after these highly technical discussions above. I promise that this is the last topic for this tutorial and guess what. It gonna be less technical and full of fun because we are going to finish on Fuzzing attacks. Yes, Fuzzing. 😊

In short, Fuzzing consists in throwing unexpected or malformed inputs at a device to make it crash or behave abnormally. It is one of the best ways to discover hidden bugs in parsers, protocol handlers or memory management code.

Fuzzing is basically the digital version of poking something over and over with a stick to see if it breaks. Hackers love it because it is a great way to uncover hidden bugs in a device by feeding it strange, unexpected or messy data and watching what happens.😂

There are two main styles of fuzzing :

• Dumb fuzzing is like smashing your keyboard, sending all that random nonsense to the device and hoping it crashes.
• Smart fuzzing is more like playing detective. It crafts inputs that are weird but still valid basically the kind of stuff that can sneak past initial checks and trigger deep bugs inside protocols or software logic.

If the device glitches, crashes or starts acting funny… this is the jackpot! 😂 But if fuzzing on a regular computer is easy and fast you can throw thousands (even millions!) of tests per second. But with embedded devices, things get tricky. They are slower, harder to observe and don’t always tell you why they stopped working. It’s like trying to debug a toaster that won’t speak. That’s where a cool trick called firmware rehosting comes in. Instead of testing the real device, you run its firmware on a PC in an emulated environment. That way, you can fuzz it much faster no need to press buttons or reboot the actual hardware every time.

Fuzzing might sound messy, but it is one of the best ways to sniff out deep bugs that can lead to real-world attacks. Think of it as controlled chaos and chaos can be pretty revealing.

CONCLUSION

And there you have it, dear networkseclearners a deep dive into the wild world of embedded hardware attacks. From poking at PCBs to sneaky power analysis, glitching CPUs, X-raying chips with electron microscopes and even confusing your poor toaster with fuzzing 😅, it is clear that hardware hacking is not just for spy movies. It is real, clever and it is happening out there.

These techniques remind us of an important truth : no matter how secure the software is, the hardware it runs on is just as critical. If attackers can pull secrets from power blips or flip memory bits by force, then we must design and defend smarter starting from the silicon all the way up to the cloud.

I hope you enjoyed this journey and that you learned something new and maybe a bit terrifying 😄. If you did, share this article with your friends, colleagues or that one hacker-minded buddy who loves reverse engineering coffee machines.

Got questions? Spotted a mistake? Want to suggest another topic? Drop a comment below and let’s keep learning and growing together as a community! I can’t wait to meet you again on the next article. Don’t forget to subscribe to the newsletter to get notified as soon as the next article is released.

Until next time, stay curious, stay safe and keep exploring for a more secure digital world. 🙏😊

REFERENCES

• Jasper van Woudenberg & Colin O’Flynn. The Hardware Hacking Handbook: Breaking Embedded Security with Hardware Attacks. No Starch Press, 2022. ISBN: 978-1-59327-874-8.

This article is largely inspired by practical concepts and real-world techniques described in The Hardware Hacking Handbook. If you’re curious to go deeper into the world of embedded hardware security, it is a fantastic technical resource worth checking out!