Ask HN: Do you worry about CPU backdoors like IME?

  • > Is the threat real, overblown, or relatively unexplored?

    There are efforts to reverse engineer it, and a lot of information is known about it.

    The problem is:

    - Intel has created its CPU to require ME for CPU initialization. So no ME, no CPU. You can neuter most of it but not the part that starts the CPU.

    - Intel has locked the space down with strong cryptography and is the only one that can create, read, put or modify code there.

    - There's no guarantee that Intel won't use or be forced to use this for a given purpose (good or bad) in the future.

    But, any ME backdoor can't really be used remotely without traversing a network. This means:

    - The ME might enable someone with physical access to the computer to have free reign through some undocumented or lesser known interfaces (like USB JTAG), but it's far more likely the OS has an exploitable vulnerability in that situation that's at least equivalent (e.g. Thunderbolt DMA). Generally, you are always screwed if your adversary has physical access to the system.

    - Theoretically you could monitor the outgoing network traffic from the system and notice anything unusual. This is difficult with most general-purpose operating systems in the way most users use them. But minimal installs of OSes (think Debian netinst) with every process accounted for and every expected network communication also accounted for could potentially be monitored enough from an external system to notice any shenanigans.

    - I don't think the ME knows how to talk to anything but the onboard Intel NICs, so you can just install a Broadcom or Realtek NIC (or a USB NIC), don't use the onboard NIC, and probably reduce any remote attack surface here significantly. This is assuming you don't install local OS drivers that allow the OS to interact with the ME over its OS-exposed interfaces and potentially get the OS to do the ME's bidding.

  • What are the implications of such hardware on user security?

    Threat persistence, i.e. persistent rootkits, persistent remote monitoring if one has privs to tickle the CPU instructions that give access. It is just a matter of time before there are public tools for script kiddies to manage the OS within the CPU. Here [1] is an example of someone slowly making progress decoding all the undocumented instructions and here is a talk with a brief overview of the tools. [2] This is not specific to Intel's ME but it is the way people will eventually tame/exploit that beast in my opinion. There are more recent talks that get deeper into security rings in the CPU. This video [3] more related to your question but not specific to ME however can be used to access ME and much more. If this appears to difficult and time consuming just know that some folks out there have the documentation for the undocumented instructions.

    You may find some tools on github and other public repos for disabling ME. Use with care. Test on an identical model of system that is at the same firmware/BIOS and same model of CPU as those tools can brick your CPU. As @rocket_surgeron stated, one can buy CPU's with ME disabled but that will not disable the "God Mode" referenced in [3].

    [1] - https://github.com/xoreaxeaxeax

    [2] - https://www.youtube.com/watch?v=KrksBdWcZgQ

    [3] - https://www.youtube.com/watch?v=jmTwlEh8L7g

  • I'm cautiously paying attention -- I don't believe they'll bring me any harm, but I'm distrusting and paranoid by nature

    As they exist today I expect you've got to be an interesting target for it to matter.

    I worry more about ten or fifteen years from now when everyone has the keys

  • I have nothing to hide, but I once read that we still prefer to put vacuous letters in envelopes than on postcards.

    I'm currently using a Raspberry Pi for my NextCloud because it's not Intel (IME), but I'm changing to a Radxa because it's more transparent.

    I (will) use a PinePhone with Biktorjg's (more) open firmware as my daily driver because the completely opaque hardware on my GrapheneOS Pixel and LineageOS OP 7T are OBVIOUSLY full of access points for state (or clever) actors.

    Not having anything to hide doesn't mean that I don't want privacy. Intel IME and the like are incompatible with that utopia.

    Please, feel free to comment on my choice of home server, the Rock 5B isn't shipping yet, there's time to change my mind.

  • Any individual can purchase a system intel ME disabled.

    Dell, System76, and Librem all sell at least some systems with ME disabled and those are just the ones I can think of without trying.

    https://puri.sm/learn/intel-me/

    https://blog.system76.com/post/168050597573/system76-me-firm...

    https://m.hexus.net/tech/news/systems/112835-dell-now-offers...

    As far as risk goes, the risk is very small and my personal opinion is that hardware is not worth replacing unless you are worried about being the target of a state-level actor who will spend the resources to gain clandestine physical access to your machine in order to surveil you.

    ME attacks require a level of sophistication that is only worth it to a small number of entities pursuing extremely important targets.

  • I operate under the belief that the governments have a crystal ball and can peer into any process at any time, they just probably aren't using it to watch you right now

  • You seem to have already made a judgement about IME and associated management processors by calling them backdoors. Intel doesn't put IME into their processors to be a back door, but to, as the name suggests, manage the processor. The fact that a malicious actor may be able to exploit the IME as a backdoor doesn't change it's actual purpose.

    The fact is that modern processors/computers are so complex that it's simply not practical to build one without some kind of initialization and management processor or other programmable device. Intel, AMD, ARM, it doesn't matter. Any processor of this size will have at least one if not more management processors.

    Maybe these companies could do better and release the source code of what runs on these management engines, and I would argue they should. But unless we want to go back 10 years in processor complexity and performance, the "Backdoors" as you call them aren't going anywhere.

  • Does Intel ME waste energy, too?

    Of course it can have security flaws, complexity that should not be required, etc, but I would expect with these messy things that it would also waste energy on unneeded features, too.

    What is needing, is computer system that does not have such features. I do not know if this will be possible as a PC with 64-bit capabilities, unless perhaps it is using RISC-V for 64-bit capabilities (in which case it is a not a "PC with 64-bit capabilities", I suppose, but rather two separate systems). An open-source implementation may be usable, possibly using emulation or FPGA for 16-bit x86 real mode, and for PC BIOS capabilities if needed. However, it is then not 64-bit x86, which means that a specialized booting is needed if you want to run operating systems other than DOS. (Another alternative is to not implement PC at all, which may also be suitable for some uses.)

  • it's totally impossible to secure computers these days. they're backdoored at the RTL for sure. for sure