Web Servers

Apache

RewriteSSL - HTTPD - Apache Software Foundation
OpenSSL: Check SSL Certificate Expiration Date and More - ShellHacks
OpenSSL - show certificate. How to check a website’s SSL certificate expiration date and view the other information from the Linux command-line.
Secure your Apache server from DDoS, Slowloris, and DNS Injection attacks
Find out which three modules to install on your Apache server to lock it down and prevent DDoS, Slowloris, and DNS Injection attacks.

NGINX

DDos Mitigation - Using NGINX to Prevent DDoS Attacks | NGINX
Learn about the features in NGINX and NGINX Plus that make them a valuable part of a solution for DDoS attack mitigation.