[Hackbraten]

Security.

It needs to be built into every phase of computing, starting with the CPU micro-code, going through network protocols, up to the topmost JS framework layer.

Screw up one piece and you may end up with a major vulnerability.

Many software project owners avoid it due to complexity. To some extent, even academia sometimes eschews it.

[thijsvandien]

There's one more layer above that: the user. That is to say it's a social problem as much as a technical one.

[sidntrivedi]

Umm..what about Compilers and their implementation? Isn't it hard?

PS: I find them the hardest.

[nikofeyn]

compilers do a known thing. security means protecting against unknown things.

[sidntrivedi]

I get your point. Seconded.