The Veriti Spottr Cybersecurity Brief

Thought Leadership Defense in Depth April 2026  ·  8 min read Moats. Drawbridges. Portcullises. Murder holes. The architects of medieval castles invented layered defense-in-depth centuries before the first computer existed — and the principles they built in stone map almost perfectly to the security posture every small business needs today. In the 13th century, the architects of Caernarfon Castle in Wales planned the King's Gate to require any visitor to cross two drawbridges, pass through five heavy doors, and pass under six portcullises — with murder holes in the ceiling and arrow slits on both walls the entire way. Though the gatehouse was never fully completed as originally designed, the intention was unambiguous: an attacker who breached the outer moat still faced the gatehouse. An attacker who forced the gatehouse still faced the portcullis. An attacker who bypassed the portcullis still faced scalding water from ab...