Sometimes your operatives steal, sometimes they destroy. I think I've even seen a combination.

This leads me to beleive its based on your own cash on hand?

If thats the case would I be right in assuming that this is a 2 stage calculation.

First figure out how much cash is 'bombed' (x) based on how much they have on hand (D)efender i'm guessing around 0.3%?

Then decided how much of that you steal and how much is destroyed - Is this based on your own cash on hand (A)ttacker

e.g

(s)tolen = x * (max(1,(A/D)))
bombed = x - s

or is there something else going on here? or is it secret sauce that we are not allowed to know?

Lots of this stuff depends on what you have on hand. Espionage does, raiding food stores does, I believe all harmful spy ops have this as a component.

Bomb banks can work in one of two different ways depending on the game server. I have updated the server details and the spy op help page to make this clearer.