Real-world software security lessons

Can common-sense and our real-world intuition show us how to write secure software?

It is a period of civil war. Rebel spaceships, striking from a hidden base, have won their first victory against the evil Galactic Empire.

During the battle, Rebel spies managed to steal secret plans to the Empire's ultimate weapon, the DEATH STAR, an armoured space station with enough power to destroy an entire planet.

Creating secure software is one of the huge challenges of the modern age. Software security is generally considered an advanced topic but I believe there are important lessons we can learn from how people secure things in the real world. By considering well-understood real-world situations and thinking about how those lessons apply to our software, we can often stumble upon security best practices.