My first job out of college was analyzing their trade sheets to see if there was any cheating. It’s been so long but trading ahead was one of the big scams. I forget what the others were called.
Giving the customers a crappy fill that was a few points away from the current price was a big one also. You will be surprised how fast I can all add up
And handing out winning commodity trades to good clients (Hillary) was also commonplace prior to rules changes.