I would be very surprised if there was any encryption, but I don't know how the tech worked, other than it was all 'dark fibre', that is, purchased links betwee

I would be very surprised if there was any encryption, but I don't know how the tech worked, other than it was all 'dark fibre', that is, purchased links between sites without any offered services. The EMC drive arrays were expensive enough that they'd be shared between projects, effectively, capacity was 'leased' to different teams within the organisation. Those drives were replicated between the sites via the fibre, so the infrastructure team responsible for that would have been doing whatever they could I guess (probably getting it working at all was the challenge rather than worrying about encryption). I do know that exchange connectivity for trading was via leased X.25 connections over the PSTN, and there was no encryption on those links. The client orders were small though, nothing to get excited about. Proper inter-bank stuff, the big bucks, were carried on the SWIFT network, which is encrypted, and that would be the place to attack if you wanted to get up to mischief. I guess that's still used today (was heavily used last time I worked in that industry 10 years ago for settlement, fx, etc)