You can now also use HTTP Auth for your solr index.

Here are the security mechanisms implemented by Opensolr.com

• IP Access rules per Request Handlers
  • Users are able to set certain Request Handlers (/select, /update, etc...) to be accessible from certain IP address, OR the "all" wildcard.
• HTTP Authentication 
  • ​Users are able to set a username and password for their index, so that every Request Handler in the index is only accessible upon valid HTTP Authentication.
• SSL connections
  • ​All connections throughout the entire Opensolr.com website, and throughout all of the opensolr cloud servers, are powered by state of the art SSL encryption.