Different Sections in Spooks

[DanielWood]

We know there are many more sections to MI5 than Section D in Spooks, here is a list of the ones I have found so far after watching the series again:
Section A - mentioned by Tom in Series 2, Episode 5
Section C - mentioned by Harry in Series 2, Episode 1
Section D - the one seen through the series
Section E - mentioned by Ruth in Series 3, Episode 9
Section G - mentioned by Malcolm in Series 3, Episode 8
Section K - seen in Series 1 headed by Tessa Phillips

Feel free to add any I've missed!

[JHyde]

From Harry's Diary we know of a few others:

Section M (conspiracy theories, rumours) - which I think would be fun sometimes and exasperating at others, and
Section X (intelligence and surveillance on MI5 officers). This section was previously headed by Oliver Mace, as I recall. I think, I haven't read Harry's Diary in a while.

We also know that Tessa headed up Section K during the 80s. Whether there was a break in service I am not sure.