I forgot the perils of assuming FedSuns competence in the Dark Ages
It is not that per se.
Intelligence operations work one way and safeguarding the operation while it goes off is pretty linear.
Analyzing intelligence- and counter-intelligence- is NOT a straight line. Best description I can think of is that you had three blindfolded people a giant box of assorted puzzle pieces and tell them to build the blue picture from the pieces of 4 puzzles. They cannot see the pieces, cannot see a picture of what it looks like put together, and can only discuss it with their fellows. MIIO could destroy all the direct data but then you get the incidentals . . . Agent X's medical file shows they had the New Samarkand Flu in 3138 and had to be hospitalized for complications on Robinson. A shipping manifest from New Avalon to Robinson in 3137 for some special Q-built gear. Huh, what "weird" happened on New Samarkand in 3137-3138. Oh, Luthien Armor Works senior engineer for particle accelerator designs drove his car off a cliff while skiing at a mountain resort but the investigation shows the vehicle was operating correctly and autopsy showed no foreign substances . . .
Methods & capabilities, a operator has no idea what single piece of information a investigator or analyst would need to put together the puzzle they are working on. Knowing how MIIO managed and executed operations in the past can give clues to how they will operate in the future as well as sealing security breaches. Consider this, a code is often times considered 'broken' when they can read 55-60% of the message which is USUALLY based on articles in the sentence, words like 'the' 'a' 'and' 'with' and other what could be considered filler. Heck even bank records if they can identify MIIO accounts- and you can start with payrolls. If they had the time & analysists, looking for/at places that show a ABSENCE of data- sats are routed so they are never overhead a certain place, flight plans all go around a area, city street & private security cameras never cover the entrance to X building, etc.
Intelligence analysis is always about pattern recognition and abstract thinking. Most spy flicks totally skip over that part, Tom Clancy was the only one I know who- in his books- covered the guys in basements with thick glasses pouring over reams of paper, looking at reference books, and cross-checking other data to fill in wholes.
Then you get into all the un-authorized information that the ISF could have scooped ups . . . some agent's private memoirs recording things that were NEVER supposed to be written down. Some government flack's insurance locked in a bank safe deposit box- which might also be a good source for blackmail on various civil service employees (Mr. Rednose, we found these interesting photos of you and this underage female in a safe deposit box. I am pretty sure your fellow citizens might . . . question . . . your tastes if these ever became public. We can ensure they do not as long as you . . . - bluntly this means Julian's gov't using folks on New Avalon could have a LOT of intelligence leaks.) think Statham's Bank Job movie- the illegal diary of a training officer at MIIO's equivalent of The Farm, copies of expense reports, souvenirs & photos of current & retired MIIO employees, and the long list of foibles human cogs have fallen for in intelligence operations.
No matter what MIIO did, there would be tons of information that COULD provide actionable intelligence.
MIIO literally could not clean up the whole world of data that the ISF could use. The difficulty will be sifting through the 99% of pointless information for the single piece that will unlock the puzzle.