Cheers! It's early 1970's british sci fi.
Grew up watching this stuff. Standard 'humanity is threatened by alien invasion' storyline. Stands for Supreme Headquarters Alien Defence Organisation. The tech, effects, and social issues were ground breaking for it's time. It is a bit dated now but mostly still stands up. Much like the original Star Trek series in the US.
The light hearted link to bitcoin/nostr/SN/Holepunch etc. is that all of us who have realised the threat to humanity posed by the current financial system are similar to the S.H.A.D.O. agents seeking to defend humanity from an existential threat...
And I honestly thought as a kid we would all be living on the moon by now!...
S.H.A.D.O.standing for?