Complex sentence: An example of such an attack on disk encryption is the "Evil Maid Attack", in which an attacker installs a bootkit on an unattended computer, replacing the legitimate boot loader with one under their control.
Split into simpler sentences: An example of such an attack on disk encryption is the "Evil Maid Attack", in which an attacker installs a bootkit on an unattended computer. The bootkit replaces the legitimate boot loader with one under their control.