^^^ So, to put the above in perspective, Paul Vernon nor his ~40 employees noticed millions of dollars worth of cryptocurrency leaving a secure platform while working in their offices on an early Tuesday morning while conducting transactions during the heist, some of which are contained in the same blocks on the blockchain.
It took Paul Vernon a year and half later to learnt from a couple Bitcoiners that five one hundred bitcoin lots were also reduced during the event while they watched it happened in virtually real time.
If I ran an exchange, I'd have a script checking for unauthorized coin movements from my cold storage wallet(s). If someone tried to steal my funds, it would instantly make a new tx with slightly higher fee, and double-spend the coin back to myself. Perhaps spend 100% as fee if the intruder were persistent...
That's just me, I'm a wily prick