If you hit Esc during a hack, you will break the console. This has a differing effect depending on the console. Crewship core shield consoles, when broken, will lower the shield without requiring the console to be hacked. Objective consoles (such as those inside a Grineer Hanger), when broken this way, will prevent progression and completion of the mission. I've only done this once, in which I hit Esc as soon as I could upon opening the hacking minigame.