Blocking /xmlrpc.php Scans in the Apache .htaccess File

Someone out there on the internet is repeatedly hitting this blog’s /xmlrpc.php service, probably looking to enumerate the user accounts on the blog as a precursor to a password scan (as described in Huge increase in WordPress xmlrpc.php POST requests at Sysadmins of the North). My access logs look like this:

176.227.196.86 - - [04/Sep/2014:02:18:19 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
195.154.136.19 - - [04/Sep/2014:02:18:19 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
176.227.196.86 - - [04/Sep/2014:02:18:19 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
176.227.196.86 - - [04/Sep/2014:02:18:21 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
176.227.196.86 - - [04/Sep/2014:02:18:22 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
176.227.196.86 - - [04/Sep/2014:02:18:24 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
195.154.136.19 - - [04/Sep/2014:02:18:24 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
176.227.196.86 - - [04/Sep/2014:02:18:26 +0000] "POST /xmlrpc.php HTTP/1.0" 200 291 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"

By itself, this is just annoying — but the real problem is that the PHP stack is getting invoked each time to deal with the request, and at several requests per second from different hosts this was putting quite a load on the server. I decided to fix the problem with a slight variation from what is suggested in the Sysadmins of the North blog post. This addition to the .htaccess file at the root level of my WordPress instance rejects the connection attempt at the Apache level rather than the PHP level:

On questions regarding ISO/DIS 18626, Information and documentation — Interlibrary Loan Transactions

There is a ballot under consideration within the ISO TC 46/SC 4 on InterLibraryLoan Transactions. The ballot description is:

This International Standard specifies the transactions between libraries or libraries and other agencies to handle requests for library items and following exchange of messages. This standard is intended to at first supplement and eventually succeed the existing international ILL standards ISO 10160, ISO 10161-1 and ISO 10161-2, which are based on the outdated open systems interconnection model. The introduction of the draft standard provides some background on the relationship of the new standard to the previous one.