If we live in a world where corporations are hacked and their IP stolen, the answer is simple. Don't keep it online.
Simple - yes. Practical - not so much. As you've probably noticed, networked computers are fairly common in today's modern space-age offices. If you airgap the network with the seekrit s0rce,
(1) you now can't do anything useful with it, like email it to manufacturing partners, send drawings to your marketing dept so they can start working on the shiny shiny brochures, and so on; and