[mikewarot]

Data diodes are connections between networks that allow passing of data in a single direction. There is no physical return channel for flow of data in the opposite direction. Usually, they come with a pair of servers that have a specialized protocol that allows continuously streaming data across the link so that users can have what appears to be a normal FTP/WEB/File server fed with information from the other side, with all the normal protocols.

Data diodes can be made for $200 or less. Commercial grade products are much more expensive.

Appropriate users would include allowing monitoring (but not control) of industrial processes.

The Office of Personnel Management should, in my opinion, have had a data diode allowing forms INBOUND only to their servers, which would have prevented a major breech.

https://en.wikipedia.org/wiki/Office_of_Personnel_Management...