In episode 1.12 "Screwdriver":   Nikki   says this code to prove that she is actually a deep cover agent for the CIA. They had approved the op where she releases a deadly virus (episode 1.01 "The Rising"), because she assured them that Mac would never let the virus be unleashed.

That is scary taking such a big risk with the lives of so many people. Her overconfidence in MacGyver's infallibility in this case concerns me. Of course it is a TV show, so I didn't expect him to fail.