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...)
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!
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.
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
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.
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.
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.
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.
>> 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.
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.
https://web.archive.org/web/20140130160743/http://datasheets...
sandsifter was lots of noisy PR, but no new encoding findings
Not a backdoor, but a documented CPU feature.
The whitepaper about rosenbridge cannot be published because it would constitute scientific fraud.
I would be even more explicit and call it “Not a backdoor, but a documented feature of ancient de facto unused Via C3 CPU.”
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.
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)
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 ...
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.
I still remember the time when mnemonics were 2 or 3 characters. Good days.
Almost exactly 8 years ago: https://news.ycombinator.com/item?id=17727140