HTTP Error Messages

[akwexavante]

Hoping someone can help me understand what's happening here. I'm getting the two error messages many many times a day from several overseas IP addresses overnight mainly.

[Tue May 11 14:08:38.917004 2021] [negotiation:error] [pid 25296] [client 39.96.139.120:41334] AH00690: no acceptable variant: /usr/share/apache2/error/HTTP_NOT_FOUND.html.var

[Tue May 11 14:08:14.349208 2021] [negotiation:error] [pid 25240] [client 39.96.139.120:45906] AH00690: no acceptable variant: /usr/share/apache2/error/HTTP_NOT_FOUND.html.var, referer: https://<My WAN Ip Address>/dns-query?dns=KhUBAAABAAAAAAAAA3d3dwZnb29nbGUDY29tAAABAAE

No idea what it is or how they are creating these error messages, is there something i should be doing here or should i just ignore them?
/usr/share/apache2/error/HTTP_NOT_FOUND.html.var does exist.

[lucy24]

Is this only showing up in error logs, or is there also something in access logs with a numerical response code? It does look like one of the more obscure 400-class errors--just the kind of thing you'd see with an inept robot that can't even put together an intelligible request.

[akwexavante]

Found the following two entries:

39.96.139.120 - - [11/May/2021:14:08:14 +0100] "POST /dns-query HTTP/1.1" 406 -
39.96.139.120 - - [11/May/2021:14:08:14 +0100] "GET / HTTP/1.0" 200 9528

[akwexavante]

I have now created a file named dns-query with some unpleasant wordage within it!

[phranque]

You must examine the Accept(*) headers in the request in order to determine why the 406 status code was thrown.

[akwexavante]

Thank you everybody for your replies.

[lucy24]

You must examine the Accept(*) headers in the request in order to determine why the 406 status code was thrown.

Or, if the quoted log excerpt is representative, dismiss it as Too bad, so sad, stupid robot couldn't get what it wanted ;)