this is pretty old by now but still very relevant. people dont look at this enough but with rising chip complexities for TPU units etc. and a shift towards poorly documented hardware like NVIDIA gives this problem new fuel.
Domas (and maybe his team or colleagues?) has put out shit tons of very interesting materials over the past years on advanced malware, implants and things like Cantor Dust which are amazing things to dive into.
using his own cpu fuzzer, msr fuzzing techniques etc. he has found, reversed and implemented attacks through hardware bugs and backdoors.
It cant be confirmed if a backdoor is malicious or for debugging but essentially the capabilities gained through them are what is important.
These techniques he shows throughout his videos are not super tricky to replicate and I can recommend people who have interest to dive into it, reproduce things and try to help in this domain to raise awareness and findings.
Another good avenu is:
Defcon 21 - Decapping Chips The Strike Easy Hard Way
People speak about supply chain issues in NPM and Pip etc. but these are much more severe and hard to detect.
Almost no one looks at it.
Most vendors totally ignore it because you cannot sell products against it. (if ud detect it u need to trash the hw so its not handy... for sales...)
I didn't know what Cantor Dust was, and had to click through a few different search results to get past all the abstract descriptions and begin to form a basic idea.
In a nutshell, I understand them as a sort of "blockie" for binary data formats. Things like WAV audio files, bitmaps, ASCII text, machine code, etc. each generate their own distinct visual signature (but different examples within any of these categories tend to generate similar signatures). So once you learn the "blockies" for different types of data, they really pop out when content is viewed this way ("hey there's an image buried in that sequence of 1's and 0's!").
The explanation on this page isn't bad, and the bitmap example near the bottom is particularly illustrative (once you've seen the reference image for bitmaps earlier in the page):
See, there's Math (which typically generates graphs, graphics, other visuals), and then there's Higher-dimensional Math (you could almost call it 'Meta-math') -- which generates graphs about graphs, graphics about graphics, visuals about previous visuals...
That is, take a math equation that generates a graph. OK, so a simple example is that we could take the derivative... That generates a second graph which gives us information about the first graph... a "graph about a graph", so to speak, a "signal about a signal", information about the original information...
Point is, Cantor Dust looks like another great mathematical tool in any Mathematician's and/or Computer Scientist's and/or Engineer's visualization/understanding toolbox!
Oh sure, bad faith actors could use it for hacking (bad faith actors could use aspects of Isaac Newton's Calculus for hacking in various contexts, heck, any mathematical tool could be exploited in specific contexts!) -- but those people I'm sure, would not have an appreciation of the sheer mathematical beauty of such things! (Why use it to hack, when you can admire the mathematical beauty?)
Also, I should point out that humanity as a whole is far from discovering every single possible method, every single equation, every single way to visualize higher dimensional mathematics...
In other words, Cantor Dust is one such method... there will no doubt be many more in the future (I'd love to see fractal visualizations of higher dimensions!), and of course, we still have yet to understand all of the "old" previously discovered math in terms of all of the possible ways it can be used to visualize higher dimensions...
A poorly documented or undocumented (debugging) backdoor in a chip marketed for ATMs and medical hardware, enabled by default, at the very least qualifies as reckless endangerment.
Not really. A properly designed network should take account for such things as unknown/irreparable flaws. An irreparable backdoor in a device can be mitigated with a gatekeeper, something akin to a firewall that will not allow a threat actor to have access to a faulty device.
The real recklessness would be allowing an ATM unfettered access to the internet on the assumption that the manufacturer has already protected the device from every known and unknown threat.
TBF the specific backdoor isn’t the point of the article. It’s a cautionary tale. The point is that practically all systems above the MCU level, and even some of those, have lower level systems that are often undocumented or not intended for use by the hardware designers, much less the end users. Those systems often have extremely low level access to system resources.
For example, I am building a device that records motion data, video, audio, and lidar imaging. Inside the 6 dollar IMU and the 12 dollar lidar sensor are powerful processors that load binary blobs provided by the manufacturer. The lidar could potentially gain access to any of the system data stored on the SPI bus, which includes the bulk storage and secondary RAM for the system. It could exfiltrate that data using its laser to anyone within a few hundred meters in the laser fov. It could also receive remote c&c over its optical sensor. The only thing that prevents that from being the case is that I trust the blob does not include the code to do those things, but it would be trivial to replace the blob with one that does.
Millions of devices are made that include basic wifi functionality. often, this comes in the form of a dedicated WiFi module. Those almost entirely consist of a powerful processor running a proprietary binary blobs, connected to some internal bus of the system that may give it access to some or all of the functions of the device, or at the very least could cause the device to malfunction. These WiFi phy modules are sub$1, pervasive, and often built in to devices that do not have any advertised connectivity features. A threat actor that has knowledge of an attack surface for that opaque blob can probably cause >50% of the connected devices built with that product to malfunction, in some cases in serious and dangerous ways, and sometimes to exfiltrate data that might be compromising or valuable.
I recently got an air purifier. The touch button controls for adjusting the fan speed didn't seem to be working, so I emailed support.
They had me download their app, link the air purifier, and give them its MAC address. Then they asked me to try pressing each of the buttons a few times and email them back. I did so, and they responded that they re-calibrated the buttons using my touch samples. It worked.
That’s insane. I actively avoid buying things that are pointlessly internet connected nowadays. An air purifier’s buttons should be simple electromechanical switches.
I guess the chance these were malicious actors is low. But if they were, they now have their name, phone number, app install (tracking + LPE opportunities), home LAN access, and voice sample. Put on your second and third tinfoil hats, and those "sensitive switches" could be pushed and pushed until full fingerprints are taken.
I am amazed that by emailing support you were able to actually get in contact with someone technical who understood the product well enough to fix the problem.
I fancy myself as a decent writer, but I suck at writing documentation. People describe reading my notes frustrating and incomprehensible. I find it much better to use AI to untangle my, admittedly, convoluted reasoning
...which along with the already publicly-known microarchitecture of the C3 makes this statement sound like total nonsense:
The rosenbridge backdoor is a small, non-x86 core embedded alongside the main x86 core in the CPU
I remember laughing at this with a few others knowledgeable in x86 when it first came out; a self-proclaimed "security researcher" who somehow failed to RTFM.
"It's documented in the datasheet" is such a weak excuse for a backdoor.
Documenting a backdoor doesn't make it not a backdoor, just means it's not a hidden backdoor.
The fact that a number of machines shipped with the backdoor accidentally enabled, and nobody noticed for over a decade shows just how dangerous even a documented backdoor can be. The oversight wasn't even detected by someone reading the manual, it was detected by a security researcher who wrote a generic tool to fuzz out such backdoors.
backdoor means a secondary access point that defeats the security features of the primary. In the door analogy, the home owner spends a ton on a lock and camera for the front door but doesn't even have a deadbolt on the back.
Every definition of a “backdoor” in computing implicitly or explicitly considers it hidden/covert.
In the house analogy you don’t see the backdoor when approaching the front. If it was just “an alternative everyone knows about and can be broken easier than the front door” then it probably would have been called “a window”.
Most login forms have a weaker option like a SMS 2FA or password reset fallback. Nobody calls it a backdoor. It’s just a crappy second front door, or window.
The Free Software Foundation (FSF) calls the update system used in Windows 10 a "back door" [1], I think because it installs updates automatically. This sounds like nonsense to me, because it implies that I installed a back door on my own machine by enabling automatic upgrades (on Trisquel).
It's meaningful that the Windows 10 install method has no (official) way to disable it, but I don't think making something optional could make it not a back door, if it was one before.
Even when automatic updates are disabled, I'm not going to be reading every update so the effect seems mostly the same, regardless of whether updates are automatic or not.
The FSF's definition of "back door" (at the bottom of the linked page) is "any feature of a program that enables someone who is not supposed to be in control of the computer where it is installed to send it commands" which leaves a lot of ambiguity with the words "supposed to be". I am not sure how to interpret this definition.
> Is there another term they could be classfied as?
As an advertised feature of the product.
Your personal definition doesn’t match the general understanding of the word and concept. By your definition every window on a house or car is a “backdoor”. Anything with an advertised fallback is a backdoor. And sometimes the “front door” is the back door: getting money from an ATM is less secure than with an ID at the bank teller.
Password resets aren't "backdoors" unless they contain a flaw the defeats any security protections. It's not just that the backdoor is less secure than the front, the backdoor has no security or is so easily defeated the security may as well not exist.
I'm surprised the hidden aspect of backdoor is so forward in folks minds. In my thinking nothing in cyber security is hidden, I drop the obviously present hidden part of backdoor definition when it's used in yhe cyber security context.
No offense but I don’t think you have a clear enough definition in your head and you’re making it up as we go along and you get challenged.
>> I'm probably mistaken, but I've always referred to password resets as backdoors
> Password resets aren't "backdoors" unless they contain a flaw the defeats any security protections.
You really have to make up your mind. It was “always” but then it wasn’t, and even as you put it you’d have been wrong almost every time to call a reset “a backdoor”.
> I'm surprised the hidden aspect of backdoor is so forward in folks minds.
Only because you misunderstand the meaning of the term, as made very clear above. Go through the wiki page for a “backdoor”.
> In my thinking nothing in cyber security is hidden
I wonder what all those security researchers do all day, with everything being so out in the open and known by everyone.
> I drop the obviously present hidden part of backdoor definition when it's used in yhe cyber security context.
You can drop it but then you’re just using the wrong definition and wrong understanding.
no offense taken. i shouldnt have included password resets in my def. it muddied the conversation. covert is part of a def, at least sometimes, but i think its still acurate to drop it. consider a machine with two copies of ssh running, one of 22 with authentication and another on 2222 with an automatic root login. the instance on 2222 would be considered a backdoor, even though its barely hidden. Swap the ports and it's an unauthenticated frontdoor, but i'd still call it a backdoor and expect everyone to know what i mean. the important part is its bypassing securit, not that its hidden.
Not really... backdoor just means something that can bypass the main security.
It's just that publicly known backdoors are of very limited usefulness, because people go out of their way to remove, disable, or avoid them. Or worse, use them for their own gains. There have been more than a few cases of governments trying to implement and enforce publicly known backdoors (with keys only the government knows), such as the Clipper cryptography chip in the 90s.
But... just because something is documented, doesn't mean it's publicly known. We have an example here of something obscure enough to be a useful backdoor (assuming someone knew about it).
And while the underlying feature might have been documented, the fact that many BIOSes enabled the feature was not documented anywhere. That does count as hidden.
It's not as clear cut as you describe it here. In the other old thread you linked there was no real consensus if this should be considered a backdoor or not.
This shows that large companies making closed-source CPUs cannot be trusted. No doubt they would add whatever the government asks them to add.
What can be done to mitigate this? One option would be to buy a large FPGA and flash it with an open-source CPU. Another would be to emulate a CPU, working with encrypted data and commands, so that even if the backdoor in a host CPU tries to overwrite memory, it would only crash the emulated OS. One more option would be to run the code in a Virtual Machine like QEMU which translates the code and prevents issuing unknown instructions.
It's not just the government. The government sneakily adds stuff they think only they can exploit, but skilled non-state actors can exploit hardware features regardless of whether it was put there by the government. And as we get widespread diffusion of increasingly capable AI, it will become easy and cheap to do for pretty much anyone, and so will defense.
Assuming bio-digital integration continues (i.e., humans keep pace with ASI via neural interfaces), the long term solution is total hardware sovereignty, aka the digital equivalent of bodily integrity and autonomy. We have to miniaturize and widely diffuse fab technology such that computer manufacturing can be done in local small businesses or even at home: automated chip fabbing, 3D printing, and assembly in one fridge-sized appliance you can buy at the nearest supermarket, and it can make parts to build another one of itself.
It's basically reproduction, but for the digital part of your body instead of the bio part. You should be able to design and fab your own custom chips, PCB, and chassis to build your neural interface from scratch, and write personal defense software that actively adapts to threats - a digital immune system. You'll also have the option to delegate some or all of that to a collective, but it would mean losing your individual sovereignty and becoming part of a larger organism in a symbiogenesis or multicellular evolution kind of way.
Buy hardware used by government computers that are rivals to your country.
So if American, buy Chinese CPUs and install Chinese Linux or HarmoneyOS Assuming there is nothing you are doing of interest to them, as that will also have back doors
After Snowden, one can only imagine the worst and think everything has a backdoor.
But unless you are a high level terrorist or other person of interest, no state organization is going to target you at this level
P.s. you say no one can trust closed source, but a lot of open source is maintained by one or two people or a small group, just takes infiltration by one or two trusted contributors to push malicious code in and unless someone looks and finds that code amongst millions of lines of code, may never be discovered (more so as mainstream media won't publish any thing)
I was thinking about something similar recently: if you bought a US govt purchased laptop like the ruggedized Dell Latitude I saw, would it be less likely to have Intel's IME enabled?
Sure but the cops aren't going to pull you over based on what you think about Chinese policy. Government do mess with people across international borders, but the capacity to do that is inherently limited.
That still doesn't resolve who is more likely to blackmail or otherwise misuse data. I think it's a Chinese saying: the mountains are high and the emperor is far away.
So is it apparent that this backdoor was intentionally added by VIA for nefarious purposes? Or is there any other reasonable explanation for its existence?
I was wondering the same, this is an ancient CPU by now, having been introduced in 2001. During development and at the introduction, most people were still running Windows 95/98/ME, which had more serious security issues (like every user essentially being admin). It may just have been a handy (debugging?) feature?
Yes there is a harmless explanation. The VIA C3 is a fairly simple CPU design that cracks x86 instructions into an internal simpler instruction format. Some complex x86 behaviour is normally implemented by lengthy microcode or complex state machines. VIA wanted to make their CPU simpler than Intel and AMD. To do that they exposed this internal instruction set to the BIOS to let it handle hardware initialisation and documented how to lock this feature safely away afterward. Some BIOS authors didn't read/understand the full specification. shrug.
IIRC there are also a few hints they at least considered exposing this alternative instruction set at runtime to get more performance out of the CPU core e.g. more useable registers, more three operand instructions, saturating and packed math for DSP workloads, etc.
Misleading, clickbait title. Technically accurate, but it would be accurate if it were 3 total cpu's rather than thousands or millions so that is a low bar.
Via C3 CPUs are the only ones affected. A security problem sure, but a relatively obscure one that doesn't effect anyone's laptop, server in the cloud, etc.
A reasonable title is "Backdoor found in Via C3 cpus".
this is pretty old by now but still very relevant. people dont look at this enough but with rising chip complexities for TPU units etc. and a shift towards poorly documented hardware like NVIDIA gives this problem new fuel.
Domas (and maybe his team or colleagues?) has put out shit tons of very interesting materials over the past years on advanced malware, implants and things like Cantor Dust which are amazing things to dive into.
using his own cpu fuzzer, msr fuzzing techniques etc. he has found, reversed and implemented attacks through hardware bugs and backdoors.
It cant be confirmed if a backdoor is malicious or for debugging but essentially the capabilities gained through them are what is important.
These techniques he shows throughout his videos are not super tricky to replicate and I can recommend people who have interest to dive into it, reproduce things and try to help in this domain to raise awareness and findings.
Another good avenu is: Defcon 21 - Decapping Chips The Strike Easy Hard Way
People speak about supply chain issues in NPM and Pip etc. but these are much more severe and hard to detect.
Almost no one looks at it. Most vendors totally ignore it because you cannot sell products against it. (if ud detect it u need to trash the hw so its not handy... for sales...)
I didn't know what Cantor Dust was, and had to click through a few different search results to get past all the abstract descriptions and begin to form a basic idea.
In a nutshell, I understand them as a sort of "blockie" for binary data formats. Things like WAV audio files, bitmaps, ASCII text, machine code, etc. each generate their own distinct visual signature (but different examples within any of these categories tend to generate similar signatures). So once you learn the "blockies" for different types of data, they really pop out when content is viewed this way ("hey there's an image buried in that sequence of 1's and 0's!").
The explanation on this page isn't bad, and the bitmap example near the bottom is particularly illustrative (once you've seen the reference image for bitmaps earlier in the page):
https://inside.battelle.org/blog-details/battelle-publishes-...
My armchair-expertise here is only about 20 minutes old, but I hope this helps someone else looking for a starting point to learn about them!
Fascinating, thanks for sharing. A candor dust guessing game would be pretty fun to play
This is excellent!
An absolutely great link!
Not so much for the hacking (White Hat, Black hat, other-color-hat) aspects (although they're certainly there too), but for the
visualization of higher-dimensional mathematics aspect...
In other words, have a look at the following URL's, then come back here:
https://gods.art/articles/equation_shadows.html
https://kettenreihen.wordpress.com/
See, there's Math (which typically generates graphs, graphics, other visuals), and then there's Higher-dimensional Math (you could almost call it 'Meta-math') -- which generates graphs about graphs, graphics about graphics, visuals about previous visuals...
That is, take a math equation that generates a graph. OK, so a simple example is that we could take the derivative... That generates a second graph which gives us information about the first graph... a "graph about a graph", so to speak, a "signal about a signal", information about the original information...
Point is, Cantor Dust looks like another great mathematical tool in any Mathematician's and/or Computer Scientist's and/or Engineer's visualization/understanding toolbox!
Oh sure, bad faith actors could use it for hacking (bad faith actors could use aspects of Isaac Newton's Calculus for hacking in various contexts, heck, any mathematical tool could be exploited in specific contexts!) -- but those people I'm sure, would not have an appreciation of the sheer mathematical beauty of such things! (Why use it to hack, when you can admire the mathematical beauty?)
Also, I should point out that humanity as a whole is far from discovering every single possible method, every single equation, every single way to visualize higher dimensional mathematics...
In other words, Cantor Dust is one such method... there will no doubt be many more in the future (I'd love to see fractal visualizations of higher dimensions!), and of course, we still have yet to understand all of the "old" previously discovered math in terms of all of the possible ways it can be used to visualize higher dimensions...
Anyway, great link!
A poorly documented or undocumented (debugging) backdoor in a chip marketed for ATMs and medical hardware, enabled by default, at the very least qualifies as reckless endangerment.
Not really. A properly designed network should take account for such things as unknown/irreparable flaws. An irreparable backdoor in a device can be mitigated with a gatekeeper, something akin to a firewall that will not allow a threat actor to have access to a faulty device.
The real recklessness would be allowing an ATM unfettered access to the internet on the assumption that the manufacturer has already protected the device from every known and unknown threat.
This backdoor only appears on decades-old VIA C3 embedded x86 processors
TBF the specific backdoor isn’t the point of the article. It’s a cautionary tale. The point is that practically all systems above the MCU level, and even some of those, have lower level systems that are often undocumented or not intended for use by the hardware designers, much less the end users. Those systems often have extremely low level access to system resources.
For example, I am building a device that records motion data, video, audio, and lidar imaging. Inside the 6 dollar IMU and the 12 dollar lidar sensor are powerful processors that load binary blobs provided by the manufacturer. The lidar could potentially gain access to any of the system data stored on the SPI bus, which includes the bulk storage and secondary RAM for the system. It could exfiltrate that data using its laser to anyone within a few hundred meters in the laser fov. It could also receive remote c&c over its optical sensor. The only thing that prevents that from being the case is that I trust the blob does not include the code to do those things, but it would be trivial to replace the blob with one that does.
Millions of devices are made that include basic wifi functionality. often, this comes in the form of a dedicated WiFi module. Those almost entirely consist of a powerful processor running a proprietary binary blobs, connected to some internal bus of the system that may give it access to some or all of the functions of the device, or at the very least could cause the device to malfunction. These WiFi phy modules are sub$1, pervasive, and often built in to devices that do not have any advertised connectivity features. A threat actor that has knowledge of an attack surface for that opaque blob can probably cause >50% of the connected devices built with that product to malfunction, in some cases in serious and dangerous ways, and sometimes to exfiltrate data that might be compromising or valuable.
That’s what this article is really about.
I recently got an air purifier. The touch button controls for adjusting the fan speed didn't seem to be working, so I emailed support.
They had me download their app, link the air purifier, and give them its MAC address. Then they asked me to try pressing each of the buttons a few times and email them back. I did so, and they responded that they re-calibrated the buttons using my touch samples. It worked.
That’s insane. I actively avoid buying things that are pointlessly internet connected nowadays. An air purifier’s buttons should be simple electromechanical switches.
I guess the chance these were malicious actors is low. But if they were, they now have their name, phone number, app install (tracking + LPE opportunities), home LAN access, and voice sample. Put on your second and third tinfoil hats, and those "sensitive switches" could be pushed and pushed until full fingerprints are taken.
I am amazed that by emailing support you were able to actually get in contact with someone technical who understood the product well enough to fix the problem.
> This backdoor only appears on decades-old VIA C3 embedded x86 processors
Modern Intel and AMD chips also have separate CPU cores that neither the user nor the installed OS control.
Intel Management Engine:
https://en.wikipedia.org/wiki/Intel_Management_Engine
AMD Platform Security Processor:
https://www.wikipedia.org/wiki/AMD_Platform_Security_Process...
Intel added them in 2008. AMD followed suit about five years later.
They should have mentioned that in the first line of the github readme, not burried deep down in the text.
Buried? Deep down? The fourth paragraph, clearly labeled "Affected Systems", a minute or two into the read.
Opening with the title "hardware backdoors in x86 CPUs" is quite misleading, though.
We have shorter attention spans now.
Multiple things can be true at the same time. While we do have shorter attention spans, some (lots of?) developers absolutely suck at writing articles
I fancy myself as a decent writer, but I suck at writing documentation. People describe reading my notes frustrating and incomprehensible. I find it much better to use AI to untangle my, admittedly, convoluted reasoning
They knew what they were doing by not including "VIA C3 CPUs" before the fourth paragraph. Come on. It should have been in the title.
Imagine getting a letter "High Risk of Cancer" and getting all the way to the 4th paragraph to see it's just relevant to a race of blue aliens...
It's not even a "backdoor", it's documented in the datasheet...
http://datasheets.chipdb.org/VIA/Nehemiah/VIA%20C3%20Nehemia... (page 82)
...which along with the already publicly-known microarchitecture of the C3 makes this statement sound like total nonsense:
The rosenbridge backdoor is a small, non-x86 core embedded alongside the main x86 core in the CPU
I remember laughing at this with a few others knowledgeable in x86 when it first came out; a self-proclaimed "security researcher" who somehow failed to RTFM.
There's even a Wikipedia article about it now, with a link to the alternate instruction set documentation: https://en.wikipedia.org/wiki/Alternate_Instruction_Set
"It's documented in the datasheet" is such a weak excuse for a backdoor.
Documenting a backdoor doesn't make it not a backdoor, just means it's not a hidden backdoor.
The fact that a number of machines shipped with the backdoor accidentally enabled, and nobody noticed for over a decade shows just how dangerous even a documented backdoor can be. The oversight wasn't even detected by someone reading the manual, it was detected by a security researcher who wrote a generic tool to fuzz out such backdoors.
Doesn’t backdoor imply hidden? If it’s clearly documented it’s just a (front)door?
backdoor means a secondary access point that defeats the security features of the primary. In the door analogy, the home owner spends a ton on a lock and camera for the front door but doesn't even have a deadbolt on the back.
Every definition of a “backdoor” in computing implicitly or explicitly considers it hidden/covert.
In the house analogy you don’t see the backdoor when approaching the front. If it was just “an alternative everyone knows about and can be broken easier than the front door” then it probably would have been called “a window”.
Most login forms have a weaker option like a SMS 2FA or password reset fallback. Nobody calls it a backdoor. It’s just a crappy second front door, or window.
The Free Software Foundation (FSF) calls the update system used in Windows 10 a "back door" [1], I think because it installs updates automatically. This sounds like nonsense to me, because it implies that I installed a back door on my own machine by enabling automatic upgrades (on Trisquel).
It's meaningful that the Windows 10 install method has no (official) way to disable it, but I don't think making something optional could make it not a back door, if it was one before.
Even when automatic updates are disabled, I'm not going to be reading every update so the effect seems mostly the same, regardless of whether updates are automatic or not.
The FSF's definition of "back door" (at the bottom of the linked page) is "any feature of a program that enables someone who is not supposed to be in control of the computer where it is installed to send it commands" which leaves a lot of ambiguity with the words "supposed to be". I am not sure how to interpret this definition.
[1] https://www.gnu.org/proprietary/proprietary-back-doors.html#...
I'm probably mistaken, but I've always referred to password resets as backdoors. Is there another term they could be classfied as?
> Is there another term they could be classfied as?
As an advertised feature of the product.
Your personal definition doesn’t match the general understanding of the word and concept. By your definition every window on a house or car is a “backdoor”. Anything with an advertised fallback is a backdoor. And sometimes the “front door” is the back door: getting money from an ATM is less secure than with an ID at the bank teller.
Password resets aren't "backdoors" unless they contain a flaw the defeats any security protections. It's not just that the backdoor is less secure than the front, the backdoor has no security or is so easily defeated the security may as well not exist.
I'm surprised the hidden aspect of backdoor is so forward in folks minds. In my thinking nothing in cyber security is hidden, I drop the obviously present hidden part of backdoor definition when it's used in yhe cyber security context.
No offense but I don’t think you have a clear enough definition in your head and you’re making it up as we go along and you get challenged.
>> I'm probably mistaken, but I've always referred to password resets as backdoors
> Password resets aren't "backdoors" unless they contain a flaw the defeats any security protections.
You really have to make up your mind. It was “always” but then it wasn’t, and even as you put it you’d have been wrong almost every time to call a reset “a backdoor”.
> I'm surprised the hidden aspect of backdoor is so forward in folks minds.
Only because you misunderstand the meaning of the term, as made very clear above. Go through the wiki page for a “backdoor”.
> In my thinking nothing in cyber security is hidden
I wonder what all those security researchers do all day, with everything being so out in the open and known by everyone.
> I drop the obviously present hidden part of backdoor definition when it's used in yhe cyber security context.
You can drop it but then you’re just using the wrong definition and wrong understanding.
no offense taken. i shouldnt have included password resets in my def. it muddied the conversation. covert is part of a def, at least sometimes, but i think its still acurate to drop it. consider a machine with two copies of ssh running, one of 22 with authentication and another on 2222 with an automatic root login. the instance on 2222 would be considered a backdoor, even though its barely hidden. Swap the ports and it's an unauthenticated frontdoor, but i'd still call it a backdoor and expect everyone to know what i mean. the important part is its bypassing securit, not that its hidden.
Not really... backdoor just means something that can bypass the main security.
It's just that publicly known backdoors are of very limited usefulness, because people go out of their way to remove, disable, or avoid them. Or worse, use them for their own gains. There have been more than a few cases of governments trying to implement and enforce publicly known backdoors (with keys only the government knows), such as the Clipper cryptography chip in the 90s.
But... just because something is documented, doesn't mean it's publicly known. We have an example here of something obscure enough to be a useful backdoor (assuming someone knew about it).
And while the underlying feature might have been documented, the fact that many BIOSes enabled the feature was not documented anywhere. That does count as hidden.
Was this documentation public at the time? The pdf still does not document the instructions themselves.
It was public at least 4 years before he first announced his discovery:
https://web.archive.org/web/20140130160743/http://datasheets...
yes, AIS was known
sandsifter was lots of noisy PR, but no new encoding findings
AFAIK, sandsifter did find a halt-and-catch-fire instruction on one of the CPUs, but I haven't seen anyone announce which CPU model it was.
The documentation was locked away behind NDAs when the faulty BIOS leaving it reachable was discovered. Look at the publication dates.
It's not as clear cut as you describe it here. In the other old thread you linked there was no real consensus if this should be considered a backdoor or not.
Also worth noting that the exploit was published nearly decade ago. Still, even at that time, those VIA CPUs were over 15 years old.
Perfect. The next the the bank's ATM "cannot process the transaction" we now have a pathway to debug the issue.
This shows that large companies making closed-source CPUs cannot be trusted. No doubt they would add whatever the government asks them to add.
What can be done to mitigate this? One option would be to buy a large FPGA and flash it with an open-source CPU. Another would be to emulate a CPU, working with encrypted data and commands, so that even if the backdoor in a host CPU tries to overwrite memory, it would only crash the emulated OS. One more option would be to run the code in a Virtual Machine like QEMU which translates the code and prevents issuing unknown instructions.
It's not just the government. The government sneakily adds stuff they think only they can exploit, but skilled non-state actors can exploit hardware features regardless of whether it was put there by the government. And as we get widespread diffusion of increasingly capable AI, it will become easy and cheap to do for pretty much anyone, and so will defense.
Assuming bio-digital integration continues (i.e., humans keep pace with ASI via neural interfaces), the long term solution is total hardware sovereignty, aka the digital equivalent of bodily integrity and autonomy. We have to miniaturize and widely diffuse fab technology such that computer manufacturing can be done in local small businesses or even at home: automated chip fabbing, 3D printing, and assembly in one fridge-sized appliance you can buy at the nearest supermarket, and it can make parts to build another one of itself.
It's basically reproduction, but for the digital part of your body instead of the bio part. You should be able to design and fab your own custom chips, PCB, and chassis to build your neural interface from scratch, and write personal defense software that actively adapts to threats - a digital immune system. You'll also have the option to delegate some or all of that to a collective, but it would mean losing your individual sovereignty and becoming part of a larger organism in a symbiogenesis or multicellular evolution kind of way.
>What can be done to mitigate this?
Buy hardware used by government computers that are rivals to your country.
So if American, buy Chinese CPUs and install Chinese Linux or HarmoneyOS Assuming there is nothing you are doing of interest to them, as that will also have back doors
After Snowden, one can only imagine the worst and think everything has a backdoor.
But unless you are a high level terrorist or other person of interest, no state organization is going to target you at this level
P.s. you say no one can trust closed source, but a lot of open source is maintained by one or two people or a small group, just takes infiltration by one or two trusted contributors to push malicious code in and unless someone looks and finds that code amongst millions of lines of code, may never be discovered (more so as mainstream media won't publish any thing)
While I do think this is a good idea, it may no longer be as good as it once was: https://journalrecord.com/2026/08/05/fbi-law-enforcement-tie...
If you’re just an average dissident, it’s probably still good advice though.
I was thinking about something similar recently: if you bought a US govt purchased laptop like the ruggedized Dell Latitude I saw, would it be less likely to have Intel's IME enabled?
If many people do this then I'm sure China will find some uses for that data at some point.
Sure but the cops aren't going to pull you over based on what you think about Chinese policy. Government do mess with people across international borders, but the capacity to do that is inherently limited.
> Sure but the cops aren't going to pull you over based on what you think about Chinese policy.
You might be surprised to learn that China has operated clandestine prisons in the US!
https://www.justice.gov/archives/opa/pr/two-arrested-operati...
Blackmail is still a possibility ...
Plus your data can be sold on the market. To US based entities. While the Chinese still hold on to the data for future uses ...
That still doesn't resolve who is more likely to blackmail or otherwise misuse data. I think it's a Chinese saying: the mountains are high and the emperor is far away.
Can't Chinese government exchange the data with your government whenever they need it?
Once you control the hosts CPU it's game over for the guest. The best you can do is to fetch old PPC G4 Apple computers or Thinkpads.
[delayed]
As noted by userbinator: https://news.ycombinator.com/item?id=49220030
Not a backdoor, but a documented CPU feature.
The whitepaper about rosenbridge cannot be published because it would constitute scientific fraud.
> Not a backdoor, but a documented CPU feature.
I would be even more explicit and call it “Not a backdoor, but a documented feature of ancient de facto unused Via C3 CPU.”
[delayed]
For Intel-ME and AMD PSP, you fundamentally can't see the backdoor they could produce unless you probe the seperate chip lol.
Or we use AI to find bug in those systems. Along with the way to completely disable those.
If you have an AI, you could make it analyze crystal photos?
Even before that, wasn't SMM the OG x86 backdoor?
You can find recorded presentations on YouTube: https://youtu.be/_eSAF_qT_FY
(2018)
And "x86" sort of gives the wrong impression -- this isn't an AMD or Intel chip; it's a 2001-era VIA chip.
Intel chips also have a hardware backdoor in the form of a separate core that the neither the user nor the installed operating system control.
Intel Management Engine:
https://www.wikipedia.org/wiki/Intel_Management_Engine
As do AMD chips:
AMD Platform Security Processor:
https://www.wikipedia.org/wiki/AMD_Platform_Security_Process...
So is it apparent that this backdoor was intentionally added by VIA for nefarious purposes? Or is there any other reasonable explanation for its existence?
I was wondering the same, this is an ancient CPU by now, having been introduced in 2001. During development and at the introduction, most people were still running Windows 95/98/ME, which had more serious security issues (like every user essentially being admin). It may just have been a handy (debugging?) feature?
Yes there is a harmless explanation. The VIA C3 is a fairly simple CPU design that cracks x86 instructions into an internal simpler instruction format. Some complex x86 behaviour is normally implemented by lengthy microcode or complex state machines. VIA wanted to make their CPU simpler than Intel and AMD. To do that they exposed this internal instruction set to the BIOS to let it handle hardware initialisation and documented how to lock this feature safely away afterward. Some BIOS authors didn't read/understand the full specification. shrug.
IIRC there are also a few hints they at least considered exposing this alternative instruction set at runtime to get more performance out of the CPU core e.g. more useable registers, more three operand instructions, saturating and packed math for DSP workloads, etc.
Should add (2018) to the title
My bad, but I don't see an edit option anymore.
Title should be: ..in VIA C3 processors.
I had not heard of VIA since the 1990's.
I am always wondering how those backdoors are discovered without internal leaks, fuzzing or enumerating all instructions bytes seem like too random.
Google “sandsifter”
"Not this shit again"...
Almost exactly 8 years ago: https://news.ycombinator.com/item?id=17727140
While the README calls it a separate core, it's more likely to be a direct encoding of uops.
A much better title would be "A hardware backdoor in a historical VIA x86 CPU".
It’s lovely to think some x86 CPUs have a nice ISA buried under the layers of cruft that form a recent x86 ISA.
I still remember the time when mnemonics were 2 or 3 characters. Good days.
Misleading, clickbait title. Technically accurate, but it would be accurate if it were 3 total cpu's rather than thousands or millions so that is a low bar.
Via C3 CPUs are the only ones affected. A security problem sure, but a relatively obscure one that doesn't effect anyone's laptop, server in the cloud, etc.
A reasonable title is "Backdoor found in Via C3 cpus".
Click bait title, please change it to VIA C3 CPUs
I recommend flagging this sort of crap to death...
Stupid autistic policy of "Don't editorialize the title"...
My bad, HN doesn't allow editing after an hour of posting
The backdoor(sic) is to delete and repost as you wipe the egg off your face.
The CPU is not the most used vector, the firmware is.
(2018)
Can we add "some ancient Via CPUs" to the title. Current title is pure click bait.
Interesting codenames: https://en.wikipedia.org/wiki/List_of_VIA_C3_microprocessors
https://www.eetimes.com/hot-25-wen-chi-chenvia-technologies/