Hi Jim-san and CodeMonkey-san.

Some of Kenmo-men invented a way to determine the crawling IP addresses efficiently.

The present system is just returning "転載は禁止です," but it's only a game of cat and mouse.
Why don't you change the system so that returns the accessing IP address on the .dat file?
If the user was an innocent, it would be just an IP checker, and if the user was a crawler, its IP address appears on the thread in .sc.
Then you will be able to find the clawlers out, and burn it easily.