Cyberwarfare: Information Operations in a Connected World, 2nd Edition

Defense in Depth

From ancient Roman fortifications to medieval castles, the concept of providing defense in depth by layering protective capabilities has been in use for thousands of years. The earliest motte and bailey fortifications used by the Norman invaders in England in the 11th century are recognizable as the predecessors of the mighty medieval castles you are probably familiar with. This design layered ditches, mounds of earth, and wooden palisades around a central multistory, defensible house (keep). The Normans ruled the recently conquered countryside from these very early castles. They relied on the multiple layers to keep them safe even if attackers successfully crossed the ditch and burned the palisade down.

Over the next 200 years, ...