Venkat's team discovered that hackers can steal data when a processor fetches commands from the micro-op cache.
"Think about a hypothetical airport security scenario where TSA lets you in without checking your boarding pass because (1) it is fast and efficient, and (2) you will be checked for your boarding pass at the gate anyway," Venkat said. "A computer processor does something similar. It predicts that the check will pass and could let instructions into the pipeline. Ultimately, if the prediction is incorrect, it will throw those instructions out of the pipeline, but this might be too late because those instructions could leave side-effects while waiting in the pipeline that an attacker could later exploit to infer secrets such as a password."
Because all current Spectre defenses protect the processor in a later stage of speculative execution, they are useless in the face of Venkat's team's new attacks. Two variants of the attacks the team discovered can steal speculatively accessed information from Intel and AMD processors.