MI 5, or simply five, is the name of one of the main security services which protect the United Kingdom. The main team of Spooks portray fictional versions of the this team. MI 5 performs internal security for the United Kingdom, dealing with threats to the security of the country that come from within it. MI 6 deal with external threats that come from other countries or organisations. The inner workings of MI 5 are split into different sections/departments which deal with problems or threats from different areas of the country.