New type spam mail filter "NNIPF" which identifies IP address nearest neighbor

This new spam mail filter "NNIPF"It is said that using nearest neighbor identification, it is more accurate than any filter that has been developed so far, and that learning ends momentarily.

Spam mail filter has been evolving rapidly since a long time ago. In the early days it was a simple thing to regard it as spam if a specific character string was included, but the whitelist / blacklist format started out and "SpamAssassinRule-based spam filters such asBayesian filterThe filtering software that adopted the dramatic power and attracted attention until 2003. However, now spammers also take measures against Bayesian filters, and it is a matter of going through one after another, no matter how much they learn.

It is said that we will filter and filter the IP address by this "NNIPF" and the nearest neighbor identification that appeared in such a situation, but what is it all about?

Details are as follows.
Slashdot Japan | SPAM Filter that performs nearest neighbor identification of IP address

It seems to be free software written in Perl. It seems that it is said that it is introduced by the administrator of the mail server rather than the introduction mainly on the user side.

The ULTIMATE SPAM Filter NNIPF (Nearest Neighbor IP address based mail filter)

As for the "nearest neighbor discrimination" touched on here, what kind of method is to explain so that the following page can be understood somehow.

ProgrammingReport. - Nearest neighbor determination rule

It seems like I do not know what it seems to be. If free software which can be easily used even by Windows users applying this comes out, it's Ureshii ... ... Who ...?