This is not a post for handling SPAM.
Please find the following Softwares you would need to install.
1. ModSecurity supplies an array of request filtering and other security features to the Apache HTTP Server, IIS and NGINX. ModSecurity is a web application layer firewall.
2. Mod_evasive prevents against ddos and scripted bots which can hammer a website. Mod_evasive is the Web Denial of Service module used in ASL. It is designed to throttle http and https connections when they reach above a specified threshold.
3. OWASP ModSecurity Core Rule Set Project: ModSecurity™ is a web application firewall engine that provides very little protection on its own. In order to become useful, ModSecurity™ must be configured with rules. In order to enable users to take full advantage of ModSecurity™ out of the box, Trustwave's SpiderLabs is sponsoring and maintaining a free certified rule set for the community. Unlike intrusion detection and prevention systems, which rely on signatures specific to known vulnerabilities, the Core Rules provide generic protection from unknown vulnerabilities often found in web applications, which are in most cases custom coded. The Core Rules are heavily commented to allow it to be used as a step-by-step deployment guide for ModSecurity™.
4. Basic Server Security Hardening Configurations.
Please find a post that I found greatly useful for managing Security at the server level:
http://www.thefanclub.co.za/how-to/how-secure-ubuntu-1204-lts-server-par...
http://www.thefanclub.co.za/how-to/how-install-apache2-modsecurity-and-m...
Sources:
http://www.modsecurity.org/
http://wiki.kartbuilding.net/index.php/Apache#mod_evasive
https://www.owasp.org/index.php/Category:OWASP_ModSecurity_Core_Rule_Set...
http://www.thefanclub.co.za/how-to/how-secure-ubuntu-1204-lts-server-par...
http://www.thefanclub.co.za/how-to/how-install-apache2-modsecurity-and-m...
http://www.thefanclub.co.za/how-to/how-disable-modsecurity-rules-drupal-...