The Machine is a mainframe computer programmed to monitor and analyze data from surveillance cameras, electronic communications, and audio input throughout New York. From these data, the Machine is able to accurately predict violent acts. Currently under control of the U.S. Government, its stated job is to foresee terrorist attacks allowing the government to forestall terrorist activity. However, the Machine can detect all future violent acts, not just terrorism. At some point in the development of the Machine, Finch created a routine that would pass on so-called "irrelevant" data to him in the form of social security numbers, via coded messages over a public telephone. Unknown to Finch, Ingram also created a routine called "Contingency" on the eve of the government handoff. It is as yet unknown what this program does, or if it is currently active.
Over the course of each episode, the viewer periodically sees events from the Machine's point of view, including an on-screen display of data about a character of interest: identification, activities, records, and more as needed. The viewer also sees the Machine's perspective as it monitors New York, including commercial flights outlined by green triangles, red concentric circles indicating no-fly zones around tall buildings, and dashed boxes marking individual people. The Machine classifies the people it watches by color-coding the boxes: white for no threat or an irrelevant threat, red or red-and-white for perceived threats, and yellow for people who know about it, including Finch, Reese, Ingram, Corwin and Root. It is from the white-boxed irrelevant threat targets that Reese and Finch draw the Person of Interest they assist.
As the series progresses, a wider governmental conspiracy revolving around the development and utilization of the Machine, known as "The Project", begins to emerge. Seemingly lead by an mysterious figure known only as "Control", an unnamed official from the Office of Special Counsel (Jay O. Sanders) begins eliminating key personnel who are aware of the Machine's existence by deploying teams of Intelligence Support Activity (ISA) operatives who believe they are acting to eliminate perceived terrorist threats on the recommendation of a department known as "Research". The members of the elimination teams are classified by the Machine using a blue box.