What is common knowledge in your field but shocks outsiders?

More than half the CO₂ emissions of the industrial age have been dumped into the atmosphere since 1990.

@davidho (IT Professional); Hackers don't typically succeed because they have insane technical skills and expensive equipment. They succeed because Linda in Accounting has a lack of critical-thinking skills and/or is careless.

@RestlessLipSyndrome @davidho
Exactly.
When I did my IT course on networks and security (15 years ago now), the lecturer asked us how we'd go about gaining hostile access to a company.

I went last (being old and grizzled). I said "Get a job there. As a temp is fine. Make them *give* you access."

Jaw drop.

By the end of the course it was in his notes.