ModSecurity - ModSecurity is an Open Source web application firewall developed by Trustwave's SpiderLabs.
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Naxsi - NAXSI means Nginx Anti XSS & SQL Injection.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
AWS WAF - AWS WAF is a web application firewall that helps protect your web applications from common web exploits.
Oikik Antispam - Oikik is a cloud-based email filtering service that works with your existing email service.