Spies working for states fall into two categories: intelligence officers and agents.
Intelligence officers are members of intelligence services. They will be highly trained in espionage techniques and the use of agents. They may operate openly, declaring themselves as representatives of foreign intelligence services to their host nation, or covertly under the cover of other official positions such as diplomatic staff or trade delegates.
Some intelligence officers may operate under non-official cover to conceal the fact that they work for an intelligence service - posing as a business person, student or journalist for example. In some cases they may operate in "deep cover" under false names and nationalities. Such spies are dubbed "illegals" because they operate without any of the protections offered by diplomatic immunity.
In the UK, an agent, more formally known as a "covert human intelligence source", is someone who secretly provides information to an intelligence officer. They will probably not be a professional "spy" but may have some basic instruction in espionage methods. An agent may be motivated by a wide variety of personal or ideological factors.
Confusion often arises between what is meant by an officer and an agent. Other countries use the same terminology in different ways. In the United States, for instance, an agent is a member of an intelligence or security agency such as the FBI or CIA. Such agencies call a covert human intelligence source an "informant" rather than an "agent."
Intelligence officers seek to gather covert intelligence directly and to recruit agents to obtain intelligence on their behalf.
The methods used by intelligence officers vary widely, and are often limited only by their ingenuity. They will often take advantage of the latest technology, using it to eavesdrop, tap telephone calls and communicate secretly. However, the human relationship between intelligence officers and their agents remains a key element of espionage.
Foreign intelligence services typically seek to establish networks of agents whom they can use over a sustained period of time, so that they can obtain a reliable flow of information. Agents operate by exploiting trusted relationships and positions to obtain sensitive information. They may also look for vulnerabilities among those handling secrets. They may be aware of flaws in their organisation's security that they can exploit.
Espionage activity is also carried out in cyberspace. Foreign intelligence services increasingly use the Internet and cyber techniques to conduct espionage against UK interests. Cyber can be an attractive method of intelligence gathering for several reasons:
Cyber also negates the need for a human agent as information gathering can be done remotely, without an intelligence officer needing to leave their desk, let alone their country.
As we become more reliant on the internet in our everyday lives the threat from cyber espionage will only increase. To that end the Government has published a UK Cyber Security Strategy. This will help the UK to retain its balance of advantage in cyberspace.
For more information on how to protect against this threat, see the website of the Centre for the Protection of National Infrastructure (CPNI).