Gathering Intelligence

The importance of intelligence

Collecting intelligence to build up as much knowledge as possible of threats to the country is at the heart of MI5’s work. 

It helps us to make decisions about how we should work, with our partners, to respond to these threats and what protective security advice the National Protective Security Authority offers. 

Why we use secret intelligence 

Although publicly available information can be helpful, usually the best way to find out about the threats posed by an organisation or individual is to obtain secret intelligence about their activities. 

Individuals planning terrorist attacks, funding terrorism or conducting espionage will rarely advertise what they are doing and will often attempt to hide their activities. Secret intelligence is often the only way to learn more about people and organisations of interest. This could include information about personnel, infrastructure, intentions, plans, and capabilities. 

If intelligence is valuable we ensure that it is recorded accurately and that it can be retrieved from our systems swiftly. If we assess that a particular threat warrants more investigation, we deploy resources to obtain further intelligence, continually adjusting our assessments in light of updated intelligence or events. 

Our principal techniques for gathering intelligence are: 

  • Covert Human Intelligence Sources (CHIS) or “agents” - agents are people who can provide secret information about the target of an investigation. Agents are not MI5 employees; 
  • Directed surveillance, such as following and/or observing someone; 
  • Interception of communications, such as monitoring emails or phone calls; 
  • Communications data (including use of bulk communications data) - information about emails, messages and phone calls, such as “how and when” they were made, which is usually obtained from communications service providers; 
  • Bulk personal data, datasets - such as the electoral roll or telephone directories- containing information about a large number of people which can be accessed in a targeted way to identify or find information about a subject of interest; 
  • Intrusive surveillance, such as putting eavesdropping devices in someone's home or car; and 
  • Equipment interference, such as covertly accessing computers or other devices. 

How we use these techniques is governed by various acts of Parliament and independently scrutinised by the Investigatory Powers Commissioner's Office (IPCO). Find out more about this legislation and the rigorous oversight which ensures we always work with the law.

Although at any one time we are likely to be conducting many investigations, only a few of the most important ones would require us to use all of the methods outlined above. Eavesdropping, for example, is not only highly intrusive, meaning our case for using it must be strong, but it is also technically complex and resource-intensive. As a result, it is used sparingly. 

Necessity and proportionality 

When using intrusive techniques to gather intelligence, our aim is always to be effective with the minimum amount of intrusion required to respond proportionately to the threat. Much of the skill of intelligence work lies in finding the right blend of techniques to meet the requirements of an investigation. Before we use our most intrusive intelligence gathering methods, which require a warrant, we must justify to a Secretary of State that what we propose to do is: 

  • necessary to protect national security, or to safeguard the economic well-being of the UK against threats from overseas, or to prevent or detect serious crime 
  • proportionate to what it seeks to achieve, meaning the intelligence gained will be sufficiently great to justify the intrusion, as well as any unavoidable “collateral intrusion” against individuals other than the target. 

The Secretary of State needs to be satisfied that the information we expect to obtain could not reasonably be obtained by any other means. 

These are important tests and we only apply for warrants where we have a strong case and this threshold is clearly met. An application for a warrant is then considered very carefully by officials before being put to the Secretary of State for a decision.