# Speculative Execution Side Channels

### Introduction

One class of side channels that draws significant attention is speculative execution side channels. Based on such side channels, communities have proposed several attack variants including ones (e.g., foreshadow) against SGX. The [foreshadow](https://foreshadowattack.eu/) attack allows an attacker to extract the data from an enclave. In response to the attack, Intel have released microcode updates.


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