Perhaps it's different on trading floors
I worked for a major private investment company and they had security absolutely all over the place. I remember propping open the door once because I had to go fetch something and had no keypass and within 30 seconds someone was over because their pager had warned them of the breach. They also had "tiger teams" whose job was penetration testing of apps. They had groups solely responsible for authentication and user sign on and security triggers plastered all over the place to detect fraud.
Everyone went through ethics training annually. Everyone was subjected to restrictions on the kinds of trades they could do with severe restrictions on traders (as opposed to programmers / managers). Everyone was required to declare and preferably move all their investments in house where they could be monitored. All gifts had to be declared and there were strict limits on the value of gifts anybody could accept in one year. Failing to comply with any of this was a disciplinary offence, possibly leading to dismissal.
Not to say they were perfect (a dwarf tossing incident paid for a client and a large fine kicked off a lot of the crackdown on ethics) but they really seemed to take it damned seriously. As I said I didn't work on the trading floor but I reckon everyone in the company and every manager had it drummed into them of the dire consequences if they let the company down. It still wouldn't stop a rogue trader but I suspect in the place I was at that they'd be very proactive in trying to find them.