To be a trusted security services professional, you must hold integrity as a top value. To have integrity means that you have strong moral values, no matter the situation. You uphold those morals whether or not anyone is around to see your actions. When you have integrity, you are honest and do the right thing, no matter what variables are at hand.
Tell a quick story about a time when you acted with integrity, even if you could have made other choices without consequence. This story could include returning a lost wallet, taking an item from a store when you know it wasn't scanned and included on your bill, or even reminding the server at the restaurant that you had two cocktails and your bill reflected just one.