I don’t know. If someone was interviewing me and asked how they should stop interview fraud, I’m pretty sure I’d wonder if they were passive-aggressively accusing me of it. At the least I’d feel self-conscious. Which would probably not be conducive to a good interview for either side.
If you approach the question transparently it would work - just explain the problem that you've had a lot of candidates trying to abuse the system and would like to get their thoughts on the issue.
