[procarch2019]

Interesting, I'll have to take a look at yubikey. I just installed a Tofino firewall with the Modbus Enforcer LSM between one of our DCS and accompanying SIS systems. We have never had a system communicate process data directly up the networks except through OPC (mostly DA, which is even more problematic for firewalls). Luckily OPC UA is now natively supported on our application, so things are starting to move in that direction.

Luckily a lot of our customers use PI, so we install the PI OPC interface on the application layer and only PI ports need to be opened to the next level.

Even more so the vendor we work with, Emerson, even has IPD firewalls to go between the DCS computers (engineering, historians, operator stations) and the I/O (what we refer to as level 2). The price tag can really jump when you implement all these security features, but an argument can easily be made that it's worth it when you consider some of our customers run batches that can be worth $500K or more per batch.