NetSpectre: Read Arbitrary Memory Over Network [pdf]
The AVX side channel is neat. It relies on power management rather than cache: after 1ms of AVX2 inactivity (no 256 bit operations being performed), it goes into a power-saving mode; the next 256-bit operation pays a ~2x cycle penalty. They get 8B/min at low error rate with AVX2.In Google Cloud, from unrelated instances, they're getting 1 byte every 8 hours (3 if the target has an AVX2 gadget). Attacks tend to get better over time, but still, that's an AES key in a few days, and it assumes one discrete target; in a real deployment, that secret might be mirrored over hundreds of instances.