Some companies, like Pinterest, use systems like "lytmus" to prevent cheating. It's a monitored VM box where you do the entire assignment inside the GUI VM. I'm sure certain trust factor guarantees prevent you from outsourcing the assignment overseas.

All that said, it's an awful system and I ragequit the take-home midway through. It's buggy, slow, lacks useful hotkeys, and basically requires you to become accustomed to a wiped Linux box without any of the tools you would typically use. Sure, you can install them - but it's a timed assessment, for crying out loud.

Finally, I suppose nothing stops you from logging in with your credentials on your authorized machine and then physically handing that machine to a paid agent.