Flush+Reload

Question 1

What type of attack is Flush+Reload?

Answer 1

It is a side-channel attack.

Question 2

How does Flush+Reload work in layman’s terms?

Answer 2

It monitors access to memory ‘lines’ in shared pages, and can only be done if the attacker has physical memory sharing with the victim.

Question 3

What makes Flush+Reload a powerful attack?

Answer 3

It is cross-core and cross-VM, allowing an attacker to scrape data off of a victim simply by sharing the same memory as the victim, even without authentication.

Question 4

What is the clflush command?

Answer 4

clflush in an instruction that evicts (or flushes) a line of memory owned by the attacker from all the cache levels, including from the shared Last-Level Cache.