Solve five of the "password cracking" puzzles presented in any gamemode on any difficulty. You are presented with a word consisting of a few letters replaced with an X. Your objective is to type the correct letters to solve the "password."
There are many methods to achieving this.
You can mash your keyboard in hopes you'll eventually hit the correct letters; you can think it out based on what the given letters tell you, or you can use the somewhat frowned upon but most successful method of an auto clicker set to click every key of the keyboard in a fraction of second (best used for the "Crack 1,000 passwords" achievement.) Whichever method you choose is up to you.