Firewall rules & secure exposure
Understand firewall ownership, narrowly scoped access rules, SELinux denials and authentication-related blocking.
How do I identify which firewall manages my Linux server?
Identify UFW, firewalld and nftables on a Linux server, distinguish running managers from kernel rules and account for provider firewalls.
Read the answer Firewall rules & secure exposureHow do I read UFW firewall rules without changing them?
Read UFW status and numbered rules, understand addresses, protocols and ordering, and compare allowed ports with actual listening services.
Read the answer Firewall rules & secure exposureHow do I allow SSH from one administrator IP using UFW?
Add a narrowly scoped UFW SSH rule for a verified administrator address and actual SSH port, then test a separate connection safely.
Read the answer Firewall rules & secure exposureHow do I allow a public HTTPS service through UFW?
Allow the intended HTTPS TCP port on an existing UFW-managed server, preview the rule and verify the application from an external client.
Read the answer Firewall rules & secure exposureHow do I remove one obsolete UFW rule without resetting the firewall?
Remove a precisely identified obsolete UFW rule, preserve management access and verify that the intended service restrictions take effect.
Read the answer Firewall rules & secure exposureHow do I check the firewalld zone protecting a server interface?
Find active firewalld zones and compare runtime with permanent rules so that you inspect the policy actually attached to a server interface.
Read the answer Firewall rules & secure exposureHow do I open HTTPS in firewalld and make the rule persist?
Add HTTPS to the correct firewalld zone, test the runtime rule and save the matching permanent rule without a disruptive firewall reset.
Read the answer Firewall rules & secure exposureHow do I inspect nftables rules without flushing or changing them?
Read nftables tables, chains and rule handles to investigate server access while preserving the active firewall and its owning manager.
Read the answer Firewall rules & secure exposureHow do I investigate an SELinux denial without disabling SELinux?
Inspect SELinux audit denials and preview file-label corrections for a specific server path while preserving the active security policy.
Read the answer Firewall rules & secure exposureHow do I check whether Fail2Ban blocked a legitimate administrator?
Inspect Fail2Ban jails and a blocked administrator address, then remove only a verified mistaken ban while preserving protection for others.
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