What do you mean by fraud? If you don't want people to get airdrop more than once there are other ways, like refusing newbies and accounts that were created after a certain date, you can only accept eth addresses with 0.1 eth, ask people to join telegram and things like that.
You can't ask people to pay for an airdrop, it's not an airdrop anymore it's an ico.
Thanks for opinion, This is not final decision