While the x86 instruction set architecture strictly defines the observable behaviour of modern CPU, its inner workings remain highly undocumented. The micro-operations that govern the processor are hidden behind a wall. Let’s break this wall using vulnerabilities of the CPU itself to build a sniffer that precisely observes the micro-architectural activity. Have you ever wanted to see what a Spectre attack looks like from inside the CPU? Come and see. We don’t like walls! This talk is based on the recent work of Brandon Falk.