Hardware Security

What countermeasure protects against external devices connected to a PC using DMA to read or write main memory without permission?

  1. ARaise the supply voltage of the external device
  2. BMake DMA transfers faster
  3. CUse an IOMMU to limit each device's DMA to memory regions the OS has permitted
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Answer: C. Use an IOMMU to limit each device's DMA to memory regions the OS has permitted

DMA lets devices read and write memory directly without the CPU, so a malicious or compromised device can read or modify OS memory and keys. This became a particular concern for devices attached through fast external ports. With an IOMMU, the OS restricts each device to the addresses it has allowed, and DMA to other locations is rejected.

  • A. Voltage is irrelevant.
  • B. Faster transfers do not prevent it.
  • C. Correct. It applies address translation and protection per device.
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More Hardware Security questions

  1. What is the idea of "defense in depth," emphasized in hardware and software security?
  2. When manufacturing many devices, why give each device its own key instead of the same key in all of them?
  3. When a CPU hardware vulnerability is discovered, which is one countermeasure applied to CPUs already shipped?
  4. Which best describes the problems addressed by hardware security?
  5. Which describes a side-channel attack?