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Why I Don’t Trust Default Firewall Rules on Linux Servers
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Every Linux distro ships with its own firewall defaults — whether that’s ufw , firewalld , or plain iptables . But in my experience, default firewall rules are never enough.
ufw firewalld iptables
Here’s why I never rely on them, and how I build firewall policies that actually protect my servers.
🚨 The Problem With Default Rules
- Too Permissive Some distros allow all outbound traffic by default — including to malicious IPs.
- Assumes “One Size Fits All” A web server and a database server shouldn’t have the same rules, but defaults often treat them the same.
- Silent Gaps Some ports stay open unintentionally (like 111 for RPC or 631 for CUPS) because they’re bundled in “trusted services.”
- No Egress Control Attackers love defaults because they almost always allow outbound C2 (command-and-control) traffic.
🔐 My Firewall Hardening Steps
1. Deny by Default
Set all inbound traffic to deny unless explicitly allowed.
With UFW:
ufw default deny incoming ufw default allow outgoing
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