A fantastic feature, but unfortunately currently broken (as in over- rather than under-zealous) for prevention levels other than 'Low': https://bugs.kde.org/show_bug.cgi?id=509990

This is the absolute perfect encapsulation of the Linux problem and the Linux appeal:

Yes, it has the magical setting to fix all of your problems and frustrations, and yes it’s a finicky broken bitch to actually get working for your use case.

I say this with love.