When you hire someone/business to come in how can you be sure they won't have a rogue employee who will backdoor your systems? Is there a way you can trust anyone? How do big corporations do it? Seems with so many possible openings that the chance of someone going rogue is very possible.
Is it best to look into doing it yourself? Do you hire your own team so you can have a trust relationship?
Basically, what steps should be taken when giving someone legal rights to hack-test your systems and network?