How to secure a Linux web server

Question

I’m tasked with ensuring our Linux-based web server is as secure as possible, and I’m looking for a thorough guide on best practices. I’ve already taken some basic steps like configuring a firewall and securing SSH, but I want to delve deeper into:

• Advanced hardening techniques, including SELinux/AppArmor configurations.
• Best practices for securing web services (e.g., Apache, Nginx) and databases.
• Regular monitoring and logging strategies to detect suspicious activity. If anyone could provide a checklist or a set of detailed recommendations for securing a Linux web server, it would greatly aid our ongoing security efforts.