[Koha] How to secure KOHA requests

Dear all, Recently we are implemented KOHA on Ubuntu 16.04 everything is fine, the server has 16GB RAM but we are always seeing lack of RAM due to this process: /usr/share/koha/opac/cgi-bin/opac/opac-search.pl Is it something which can be restricted ? can we secure the requests to KOHA services using Apache ? Thank you very much in advance for any suggestion or help. Rgards,  Wahi