What stable hardening steps for Linux web servers balance security and uptime?

[Jonathan_J]

I've been tasked with hardening our company's new Linux web servers before they go into production, and I'm building a checklist beyond just basic firewall rules and SSH key authentication. I need to ensure compliance with a stricter security framework this time. I'm looking at implementing mandatory access controls like SELinux, setting up a centralized logging server, and automating vulnerability scans, but I'm worried about breaking critical services. For sysadmins who have recently gone through a thorough server hardening process, what were the most impactful yet stable changes you implemented? Are there specific tools or scripts you used to audit and enforce configurations, and how did you balance security with maintaining operational functionality for your applications?

[Brandon_P]

Two quick realities: start with a minimal, verifiable baseline and validate changes in a staging environment before touching production. A stable win is to adopt a recognized hardening baseline (CIS or equivalent) and implement it in small, iterative steps. Here are practical steps that tend to be stable across many stacks:

- Enable a Mandatory Access Control (MAC) framework appropriate for your distro. If you’re on RHEL/CentOS/Alma/Rocky, use SELinux in enforcing mode with a tailored policy; on Debian/Ubuntu, AppArmor is the equivalent. Start with the built-in, vendor-supported policies and gradually refine with semanage/aa-complain components. Keep auditd enabled to log AVCs or denials and review them in a staging environment first.
- Harden SSH and services: disable root SSH login, use key-based authentication, limit user access, and enable multifactor authentication where possible. Close or relocate nonessential services exposed to the internet.
- Centralized logging: forward logs to a dedicated log server with TLS and proper retention. Use rsyslog or syslog-ng on the host, ship to a SIEM or a local Elastic/EFK stack, and ensure time synchronization (NTP) across nodes.
- File integrity and configuration drift: run a periodic AIDE/Tripwire scan and keep a change-management record of critical configs to catch unauthorized changes.
- Regular vulnerability scanning: integrate lightweight, non-disruptive scans into your cadence (e.g., weekly OpenVAS/OpenSCAP checks) and plan patching cycles with a staging environment before prod.

If you want, I can tailor the specifics to your distro and stack (web server, containerization, etc.).