Blue Pill is the codename for a rootkit based on x86 virtualization. Blue Pill originally required AMD-V (Pacifica) virtualization support, but was later ported to support Intel VT-x (Vanderpool) as well. It was designed by Joanna Rutkowska and originally demonstrated at the Black Hat Briefings on August 3, 2006, with a reference implementation for the Microsoft Windows Vista kernel.
The name is a reference to the red pill and blue pill concept from the 1999 film The Matrix.