7 ms·

> there is no malicious piece of hardware that the attacker tricks you into using > All the attacker needs is 5 minutes alone with the computer, a screwdriver,

> there is no malicious piece of hardware that the attacker tricks you into using > All the attacker needs is 5 minutes alone with the computer, a screwdriver, and some easily portable hardware. Just started reading, but the comparison is already a little bizarre. It almost seems like the digital version of "This murderer is on the loose and you're in danger! He doesn't need to inject poison into your food. All he needs is just 5 minutes in front of you with a knife!"

DiabloD3 6y ago
I think that was the point.
- mehrdadn 6y ago
  Then I guess the comparison didn't help, but what I'm trying to say is, hidden threats are harder to protect against, not easier. Telling me I need to watch out for a threat because it's visible doesn't make any sense. You tell people to be more on alert for hidden threats, not for obvious ones.
ashtonkem 6y ago
As a general rule, anyone with physical access to your machine already owns it. Physical security matters, a lot. That being said, malicious hardware is a problem. A hacked phone charging terminal at the airport could certainly be a serious problem if there are enough vulnerabilities in the USB stack.
- nneonneo 6y ago
  Please tell this to the Intel SGX folks. They don’t seem to have gotten that memo yet...
  - numpad0 6y ago
    There are always people who “need” physically tamper proof software, and in a free state you’re free to express such demands. Intel isn’t the first nor the last. Like so: https://youtu.be/BKorP55Aqvg https://youtu.be/BKorP55Aqvg
    - ashtonkem 6y ago
      Tamper resistant.
- mjg59 6y ago
  > As a general rule, anyone with physical access to your machine already owns it. People frequently say this, but never really explain it. As far as I can tell, it translates to "Nobody cares about physical security" - except it's clear that people /do/. Things like Boot Guard are only really relevant to physical attacks. DMA protection in firmware is only really relevant to physical attacks. It's extremely obvious that the industry is attempting to avoid short term physical access to a device being sufficient to compromise it, and research that demonstrates that it's still possible is valuable.
  - zinodaur 6y ago
    An example: Macbook chargers these days have charge ports that are also used for USB devices. This means that if a user plugs in a compromised "charger", it can set its own HID type (and pretend it is a keyboard or a mouse), open a terminal and start typing malware into the computer. All of this is a bit silly though, because physical intervention implies a level of commitment that lends itself to more reliable approaches: https://xkcd.com/538/ https://xkcd.com/538/
    - mjg59 6y ago
      And a thing you can do for machines that have built-in keyboards is refuse to enable new HID devices until the user provides affirmative consent. The people who have reason to care about these attacks have defenses, and research that demonstrates those defenses are incomplete is useful research.
      - zinodaur 6y ago
        Yeah thats a good point - I personally have the bad habit of clicking "yes" to that dialogue whenever I see it, since it does sometimes spuriously appear. I certainly wouldn't attempt a teardown of all of the equipment currently plugged into my machine when I saw a message like that. Do you know if HIDs can impersonate other HIDs? E.g., if you attached a dongle to a usb keyboard, could that dongle claim the identity of the keyboard and thereby avoid the prompt? My favorite "security interface failure" is the fact that OSX apps frequently demand a user login and password in a popup window. E.g., Slack does this. It would be so easy for an app render this popup (even on a webpage!) and I would totally type my password into it. I feel like the only answer to this is to have a sacred corner of the screen that only the OS is allowed to write to
kichik 6y ago
If all it takes is a malicious Thunderbolt device, why is a screwdriver needed?
- tptacek 6y ago
  Because they need to open up the victim's device to read its TB3 configuration directly off the SPI flash that holds it; that's how they get the malicious device to work in the first place.
  - boxed 6y ago
    That seems a bit counter to "Thunderspy is stealth, meaning that you cannot find any traces of the attack". No traces on the computer sure, but breaking apart my screen might be possible to see.
    - withinboredom 6y ago
      Unless they opened it before you even receive the device.
  - redactions 6y ago
    Many smaller devices do not require tools and are trivial to clone. Any of the victim devices will do. It's not only useful to attack a target computer. Device identifiers and capabilities are not bound to the security level secret values. Drop off a pre-cloned video adapter in a conference room. If it is used and as a result authorized by a targeted computer at a later moment in time, it's game over. An attacker may now perform DMA operations unless the system has kDMA protection enabled. This requires kDMA support in the BIOS, IOMMU hardware, and in the Operating System. The focus on DMA is however missing a very important observation about security levels from the research: There is a lot of attack surface when you're able to plug in a PCI(e) device as easily as a USB disk.
    - tptacek 6y ago
      You almost certainly know more about this than me, but hasn't macOS been breaking this attack --- malicious PCIE DMA --- for several years now with its IOMMU configuration? Ivan Krstic has a whole series of BH slides about this, and in the context of T2. The point about attacking trusted devices and pre-cloning devices is well taken.
lidHanteyk 6y ago
What they're trying to get across is that this is not a Bad USB [0] attack, but an Evil Maid [1] attack. In either case, the attacker does not need to rush. To commit a Bad USB attack, the attacker deputizes you and uses your confusion [2] to get you to insert a dangerous peripheral device, on your own time. In an Evil Maid attack, the attacker patiently waits until you trust (read as: "are vulnerable to") their physical presence, and then inserts a dangerous peripheral device. To use your analogy, in the former case, the murderer poisoned your food at the grocer's, and you unwittingly dose yourself when you make your meal. In the latter case, the murderer spends time getting to know you and letting you trust them, and then one day, when you go to the bathroom, they come in and shoot you like Vincent Vega. [0] https://en.wikipedia.org/wiki/USB_flash_drive#BadUSB https://en.wikipedia.org/wiki/USB_flash_drive#BadUSB [1] https://en.wikipedia.org/wiki/Evil_maid_attack https://en.wikipedia.org/wiki/Evil_maid_attack [2] http://www.cap-lore.com/CapTheory/ConfusedDeputy.html http://www.cap-lore.com/CapTheory/ConfusedDeputy.html

DiabloD3 6y ago

I think that was the point.

mehrdadn 6y ago
Then I guess the comparison didn't help, but what I'm trying to say is, hidden threats are harder to protect against, not easier. Telling me I need to watch out for a threat because it's visible doesn't make any sense. You tell people to be more on alert for hidden threats, not for obvious ones.

ashtonkem 6y ago

As a general rule, anyone with physical access to your machine already owns it. Physical security matters, a lot. That being said, malicious hardware is a problem. A hacked phone charging terminal at the airport could certainly be a serious problem if there are enough vulnerabilities in the USB stack.

nneonneo 6y ago
Please tell this to the Intel SGX folks. They don’t seem to have gotten that memo yet...
- numpad0 6y ago
  There are always people who “need” physically tamper proof software, and in a free state you’re free to express such demands. Intel isn’t the first nor the last. Like so: https://youtu.be/BKorP55Aqvg https://youtu.be/BKorP55Aqvg
  - ashtonkem 6y ago
    Tamper resistant.
mjg59 6y ago
> As a general rule, anyone with physical access to your machine already owns it. People frequently say this, but never really explain it. As far as I can tell, it translates to "Nobody cares about physical security" - except it's clear that people /do/. Things like Boot Guard are only really relevant to physical attacks. DMA protection in firmware is only really relevant to physical attacks. It's extremely obvious that the industry is attempting to avoid short term physical access to a device being sufficient to compromise it, and research that demonstrates that it's still possible is valuable.
- zinodaur 6y ago
  An example: Macbook chargers these days have charge ports that are also used for USB devices. This means that if a user plugs in a compromised "charger", it can set its own HID type (and pretend it is a keyboard or a mouse), open a terminal and start typing malware into the computer. All of this is a bit silly though, because physical intervention implies a level of commitment that lends itself to more reliable approaches: https://xkcd.com/538/ https://xkcd.com/538/
  - mjg59 6y ago
    And a thing you can do for machines that have built-in keyboards is refuse to enable new HID devices until the user provides affirmative consent. The people who have reason to care about these attacks have defenses, and research that demonstrates those defenses are incomplete is useful research.
    - zinodaur 6y ago
      Yeah thats a good point - I personally have the bad habit of clicking "yes" to that dialogue whenever I see it, since it does sometimes spuriously appear. I certainly wouldn't attempt a teardown of all of the equipment currently plugged into my machine when I saw a message like that. Do you know if HIDs can impersonate other HIDs? E.g., if you attached a dongle to a usb keyboard, could that dongle claim the identity of the keyboard and thereby avoid the prompt? My favorite "security interface failure" is the fact that OSX apps frequently demand a user login and password in a popup window. E.g., Slack does this. It would be so easy for an app render this popup (even on a webpage!) and I would totally type my password into it. I feel like the only answer to this is to have a sacred corner of the screen that only the OS is allowed to write to

kichik 6y ago

If all it takes is a malicious Thunderbolt device, why is a screwdriver needed?

tptacek 6y ago
Because they need to open up the victim's device to read its TB3 configuration directly off the SPI flash that holds it; that's how they get the malicious device to work in the first place.
- boxed 6y ago
  That seems a bit counter to "Thunderspy is stealth, meaning that you cannot find any traces of the attack". No traces on the computer sure, but breaking apart my screen might be possible to see.
  - withinboredom 6y ago
    Unless they opened it before you even receive the device.
- redactions 6y ago
  Many smaller devices do not require tools and are trivial to clone. Any of the victim devices will do. It's not only useful to attack a target computer. Device identifiers and capabilities are not bound to the security level secret values. Drop off a pre-cloned video adapter in a conference room. If it is used and as a result authorized by a targeted computer at a later moment in time, it's game over. An attacker may now perform DMA operations unless the system has kDMA protection enabled. This requires kDMA support in the BIOS, IOMMU hardware, and in the Operating System. The focus on DMA is however missing a very important observation about security levels from the research: There is a lot of attack surface when you're able to plug in a PCI(e) device as easily as a USB disk.
  - tptacek 6y ago
    You almost certainly know more about this than me, but hasn't macOS been breaking this attack --- malicious PCIE DMA --- for several years now with its IOMMU configuration? Ivan Krstic has a whole series of BH slides about this, and in the context of T2. The point about attacking trusted devices and pre-cloning devices is well taken.

lidHanteyk 6y ago

What they're trying to get across is that this is not a Bad USB [0] attack, but an Evil Maid [1] attack. In either case, the attacker does not need to rush. To commit a Bad USB attack, the attacker deputizes you and uses your confusion [2] to get you to insert a dangerous peripheral device, on your own time. In an Evil Maid attack, the attacker patiently waits until you trust (read as: "are vulnerable to") their physical presence, and then inserts a dangerous peripheral device. To use your analogy, in the former case, the murderer poisoned your food at the grocer's, and you unwittingly dose yourself when you make your meal. In the latter case, the murderer spends time getting to know you and letting you trust them, and then one day, when you go to the bathroom, they come in and shoot you like Vincent Vega. [0] https://en.wikipedia.org/wiki/USB_flash_drive#BadUSB https://en.wikipedia.org/wiki/USB_flash_drive#BadUSB [1] https://en.wikipedia.org/wiki/Evil_maid_attack https://en.wikipedia.org/wiki/Evil_maid_attack [2] http://www.cap-lore.com/CapTheory/ConfusedDeputy.html http://www.cap-lore.com/CapTheory/ConfusedDeputy.html