https://www.truthcontrol.com/articles/top-100-conspiracy-theories-all-time

3 World Wars Planned Years In Advance

The FBI (Fedral Bureau of Investicgation) deals with internal US affairs where as the

CIA (Central Itelligence Agency) is focused on external (to the US) matters.
The FBI picks up internal crimes which are covering more than one state, Organised crime, Drug trafficking and National terrorosim.
The CIA handles Foriegn intelligence, International terrorisim and threats from external states / organisations etc
They also have the NSA (National Security Agency) which is responsibe for moniotoring foreign and national communications

which in the UK is spread across MI5 and MI6.

What is the difference between MI5 and MI6?

MI5 - Counter-intelligence
MI6 - Foreign intelligence gathering

The Security Service (MI5), based at Thames House in London, is the UK's security intelligence Agency, responsible for protecting the UK,

its citizens and interests, at home and overseas, against the major threats to national security. Eliza Manningham-Buller

is responsible for the work of the Security Service, for which the Home Secretary has Parliamentary accountability.

Meanwhile, the Secret Intelligence Service (MI6), based at Vauxhall Cross in London, is primarily responsible for gathering intelligence

outside the UK in support of the government's security, defence, foreign and economic policies.

John Scarlett is responsible for the work of SIS, for which the Foreign Secretary is accountable in Parliament.

MI (Military Intelligence) had agencies numbered up to 19, but not all at the same time.

Most were folded into MI5, MI6 or GCHQ after the war.

I've found the following after a few web searches:

MI1 (Codebreaking), MI2 (Russia and Scandinavia), MI3 (Eastern Europe), MI4 (Aerial Reconnaisance), MI8 (Military Communication Interception),

MI9 (Undercover operations), MI10 (Weapons analysis) MI14 and MI15 (German specialists),

MI19 (PoW debriefing), MI17 (Military Intelligence "Head Office").

Conspiracy theorists will have you believe that there is still a clandestine MI7 dealing with matters extraterrestrial.

Logo of British Intelligence with Illuminati all-seeing-eye. MI5 created Muslim Brotherhood a century ago.