Their findings reveal a weakness in an important assumption behind existing processor security measures. To prevent this, modern security defenses can clean or isolate the processor’s prediction machinery before it is used. Code executed during that interruption could then change the processor’s prediction state after it had already been cleaned. On an AMD computer running a current Linux kernel, the researchers built an attack capable of reading protected memory at about five bytes per second. The study highlights a difficult reality of modern computer security: Even a vulnerability lasting only a few nanoseconds can sometimes be enough for a carefully designed attack.