Pretty neat concept and code (link and desc below)
https://github.com/AlexWebr/evilmaid_chkdsk
Evil Maid CHKDSK
This is s simple 512-byte MBR program that pretends to be Windows CHKDSK. It asks the user for a password, writes that password back to the media it booted from, renders that media unbootable, and reboots.
Terminal capture of using it with QEMU: http://ascii.io/a/1201
Video demonstration on a Windows laptop: