Dual networks as a security strategy
It might seem extreme, but this company's security strategy involves having two completely separate networks: one that's used for Internet activities and another, completely separate one that's used for storing sensitive client data and doing engineering work. The company, Cryptography Research, even goes so far as to put two separate systems on each employee's desktop. It might cost more, but they're satisfied with their solution of parallel networks and systems, and believe the peace of mind that comes with knowing their sensitive information is not exposed to threats is well worth it.
For more details about how they make it work, see How One Company Stays Safe with Two Networks: