Learn Russian: Тебе надо сделать резервную копию, как бы не случилась утечка. - You need to make a backup copy, lest a leak happen.

This is the core rule for clauses of apprehension with как бы не (lest / in case). Even though it refers to a potential future event, the verb must be in the past tense. This is because the particle бы always requires the past tense, just like in conditional sentences.

Does как бы не mean the exact same thing as чтобы не here?

They are very similar, but как бы не specifically expresses fear or apprehension about something out of your control ('lest' or 'for fear that'). Чтобы не is more about a direct, planned purpose ('so that it doesn't'). You use как бы не to warn against undesirable, spontaneous events.

Why is the verb случилась placed before the subject утечка?

In Russian, placing the verb before the subject is very common when introducing a new, spontaneous, or unpredictable event into the conversation. Saying как бы не случилась утечка sounds more natural and emphasizes the sudden occurrence of the leak better than как бы не утечка случилась.

Is резервную копию only used for computer data backups?

While it is the standard IT term for a data backup, резервная копия literally means 'reserve copy'. It is also perfectly natural to use it for physical things, like a spare copy of a contract or a backup set of keys.