@wakame
No, it will not teach anything. This has been discussed to some extend in the public NTP server community. My take-away: There is nothing short-term that can be done to rectify the situation.
There's a "kiss of death" packet defined in the protocol, which you can send to badly programmed rogue clients (it contains no usable time info), or you can ignore their requests. Either will cause many to simply send more requests without exponential backoff.
@niconiconi