A new security vulnerability named "Thunderclap" severely compromises security of computers with USB type-C Thunderbolt ports, or machines with Thunderbolt 3 (40 Gbps) ports. This would be pretty much every MacBook released in the past two years, Macs, and PCs with certain aftermarket Thunderbolt 3 adapters. Chronicled in a paper by the Department of Computer Science and Technology at the University of Cambridge, Rice University and SRI International, is a method for Thunderbolt devices to bypass the host machine's IOMMU (I/O memory management unit), and read its main memory over DMA.

An IOMMU translates address-spaces between devices and main memory, and hence protects your memory's contents being read by just about any device. The group has detailed possible ways to mitigate this vulnerability, and forwarded these mitigations to Apple, Intel, and Microsoft. For now no public mitigation exists other than disabling the Thunderbolt controller of your machine in your motherboard's UEFI setup program.