Then you audit the process and the work often.
simple example: what if you are the person to take, process and finalize orders at a company? You can take all their money. If you split these into 3 separate tasks, none of them can do anything. (because social factors will have more chance to keep the 3 in normal working order, where only 1 is easily to corrupt without 2 other holding them steady.)
It's unbeleivable such large coorporations still have these kind of issues. over complicated structures in my opinion, where people stop seeing the forest through the trees so to speak, and lose sight of these important matters.
While working at IBM, there was a bit of fanfare for someone in my dept who got a very big promotion (iirc, he skipped a couple levels up at once). The promotion was because he'd noticed a flaw in the system that could have allowed four people to collectively conspire and get away with maybe $6 million. He reported it and the managers were all suitably impressed. I never managed to get enough details to understand the potential scam, or the solution implemented.
Contrast this with the much larger amounts at stake with this sweepstakes & fast food org, and they aren't putting in any such multi-party controls. No surprise they were scammed.
Design the org so that power is separated, no one has the opportunity to steal at scale.
Power corrupts, absolute power corrupts absolutely. Divide the power and you remove the impetus for corruption. I don't think that cop would have done anything but an ordinary good job, had that multi-million dollar temptation not just showed up in his lap...