How does MI5 tackle espionage?

The Security Service has a dedicated branch (see organisation chart) which is responsible for counter-terrorism and counter-espionage work. We currently utilise 5% of our resources on counter-espionage. We are also heavily engaged in protective security work, which helps to counter both terrorism and espionage. See Our Major Areas of Work for more details.

Our responsibilities for counter-espionage work are defined in the Security Service Act 1989 (new window), which states:

§2) The function of the service shall be the protection of national security and, in particular, its protection against threats from espionage, terrorism and sabotage, from the activities of agents of foreign powers and from actions intended to overthrow or undermine parliamentary democracy by political, industrial or violent means.

§3) It shall also be the function of the Service to safeguard the economic well-being of the United Kingdom against threats posed by the actions or intentions of persons outside the British Islands.

We work to counter foreign espionage through a number of routes. For instance, we seek to:

• assess the level and source(s) of the threat;
  
• identify foreign intelligence officers and their agents;
  
• monitor their activities;
  
• discourage and disrupt attempted spying; and
  
• work with possible targets to help them to maintain their own security.

The ultimate aim of our work is to make it as difficult as possible for foreign spies to operate on British soil.

The fight against foreign espionage is not just a matter for MI5. We also work closely with the Secret Intelligence Service (SIS), Government Communications Headquarters (GCHQ) and other security and intelligence organisations in the UK and overseas.