What are these entries in the log file - " query: . IN NS +"?

Tue Jan 27 10:59:41 UTC 2009

On Tue, Jan 27, 2009 at 11:50:51AM +0100,
 Jan Buchholz <96devil at googlemail.com> wrote 
 a message of 38 lines which said:

> i think disable queries at the root-zone for not internal networks
> is another answer for this problem .

Good practices about this attack (with specific BIND advice) is
already there:

https://www.dns-oarc.net/oarc/articles/upward-referrals-considered-harmful