Have you ever discovered fraud in an audit?

"I've encountered that in the past and it was a rare moment in my career. I took it to the CFO, who dealt with it directly after we traced it to the source. It was handled legally and our company was better for it."

This is a yes or no question. You shouldn't dig too deep into it because you've likely signed a NDA and providing details would be inappropriate. If they do ask for details, give broad answers that don't disclose major details.

If you've never discovered any fraud, that's something to celebrate.

"I've discovered discrepancies that were later revealed to be attempts at fraud. I escalated it and upper management resolved it. Unfortunately, I signed an NDA so that's all I can say on the matter."