Person of Interest2011

John Reese:
You didn't do this yourself?

Harold Finch:
I couldn't. I'd locked myself out. The machine was designed to accept alterations in its programming only as a response to an attack. I knew that sooner or later someone would try to take it over, but I didn't know who. So I made sure that when they did they'd do it with my code.

John Reese:
You hid a virus within a virus.

Harold Finch:
I realized that the people Nathan and I had entrusted the machine to were the wrong people and that the only way to protect it would be to teach it to protect itself. I didn't want to involve you in this business, Mr. Reese, because I had hoped that, if I hadn't returned, you would continue what we had started.