I've changed it under /etc/apache2/apache2.conf. I could not see any changes. I have rebooted Apache.
I have added under /etc/apache2/apache2.conf
ServerSignature Off
ServerTokens Prod
Header:
HTTP/1.1 200 OK Date: Tue, 27 Jun 2017 14:39:42 GMT Server: Apache X-Powered-By: PHP/7.0.20 P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM" Expires: Wed, 17 Aug 2005 00:00:00 GMT Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0 Pragma: no-cache Set-Cookie: 9979992104c464a6cf7609dd3f830a86=o22c3k59ohhchujkopl1v21gj1; path=/; HttpOnly Last-Modified: Tue, 27 Jun 2017 14:39:42 GMT Vary: Accept-Encoding Content-Encoding: gzip Content-Length: 8521 Content-Type: text/html; charset=utf-8
I have Ubuntu 14.04.5 LTS