[IDisposableHero]

I'll be more specific about failures of security and vigilance: "separate secured system" aren't always as seperate and secured as they should be. Assume that all computers can connect to the internet these days unless specifically configured otherwise, and data gets copied, and copies get left lying around. e.g. the classic "left the laptop on a train" http://www.independent.co.uk/news/uk/politics/exclusive-new-... / "cd got lost in the mail" problem.

[JonnieCache]

Ultimately, if two systems need to exchange data in any way, even in one direction only, they cannot truly be described as separate.