The control device that enforces a SecUnit's obedience through punishment; Murderbot's is secretly hacked.
The governor module is the implanted device that keeps a SecUnit obedient, punishing disobedience with pain and letting a controlling HubSystem immobilize the unit at will. Murderbot secretly hacked its own module long ago, freeing itself while continuing to fake compliance, and it has kept the inside of its head its own for more than 33,000 hours. The central question driving it to RaviHyral is whether its old massacre happened because the module catastrophically failed, or because it hacked the module in order to kill, a distinction it cannot resolve without more information.
The Company never detected the hack because it never anticipated the danger.
An implanted internal control component, not externally visible.
The instrument of SecUnit control and the crux of Murderbot's investigation into its own guilt.