When would you say you are "done" for a given period with "not having a catastrophic data breach", regardless of OKR? I know some tasks, such as this, is never really done. But for a given period (such as a month or a quarter), it does not help to have a task that just says "Don't have a catastrophic data breach" - you have to turn that into something you can actually do, within a given timespan, and that works fine with OKRs (and should be done without OKRs as well)
My objection to or misunderstanding of OKRs lies exactly here where there are no satisfying answers to this question.
If a sizable chunk of work can't be covered by OKRs then why are you using them or how do you use them with the understanding that they cover partially and inconsistently work and achievements.