MI5: Britain's Spies

The official name of the agency responsible for monitoring and responding to foreign intelligence threats is the Security Service. Popular culture still refers to this organization shrouded in secrecy as the MI5, but in reality, the organization has not been officially named MI5 since 1929. MI5 stands for Military Intelligence, Section 5. As threats against the United Kingdom and the rest of the world began to change, the MI5 changed its name to the Defense Security Service in 1929 and has been known only as the Security Service since 1931. While not the official name, MI5 is used as an accepted abbreviation to "Security Service", both within the government and without.

The broad mission of the MI5 is to counter covertly organized threats to the United Kingdom. This broad mission statement lends itself to the allocation of organizational resources, of which, 91% of resources is dedicated to counter-terrorism and security, 3.5% to counter-espionage, 2% to external assistance, 3% to counter-proliferation, and 0.5% to "other threats". Next to terrorism, countering threats of espionage to the United Kingdom is still a very serious mission within the organization. While the threat of espionage from a foreign nation has been diminished greatly since the end of the cold war, the MI5 admits that espionage has simply moved into the private sector. What this means is that those who seek to harm a nation are now targeting the secrets of businesses and corporations. This is especially true in the case of defense contractors developing advanced technology for military operations.

In order to accomplish its goals, the MI5 will cooperate with other agencies to seek counter threats. Agents of the MI5 focus on investigating suspect individuals and organizations, acting to counter sources of threats while compiling evidence to charge suspects, acting in an advisory type role to keep the government of the UK and others informed of threats, and assisting other agencies in the UK and abroad.

Contrary to popular belief, the MI5 is a highly regulated organization and is bound by the laws of the Security Service Act of 1989. The purpose of the act and the oversight by the government is to ensure that the civil and privacy rights of citizens are not violated in the interests of national security.

The MI5, because of their secrecy, has been the target of various rumors and urban legends about what they do. The MI5 maintains that they do not carry out assassinations, they are not a "secret police" force (they have no powers to arrest or detain), and they do not "vet" every government employee or members of parliament.

In many ways, the MI5 is similar to the American Central Intelligence Agency. It is an organization comprised of dedicated and patriotic civilians to seek to ensure that their homeland is free from foreign threats. Citizens of the United Kingdom may not always see the effects of the MI5, but they can rest assured that the organization is doing everything in its power to keep them safe.
Sources:

About Us. Security Service, MI5