This content originally appeared on DEV Community and was authored by Faruk
Member-only story
Why I Don’t Trust Default Firewall Rules on Linux Servers
--
3
Share
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
👉 Read Full Blog on Medium Here
This content originally appeared on DEV Community and was authored by Faruk
Faruk | Sciencx (2025-09-24T22:37:10+00:00) Why I Don’t Trust Default Firewall Rules on Linux Servers | by Faruk Ahmed | Sep, 2025. Retrieved from https://www.scien.cx/2025/09/24/why-i-dont-trust-default-firewall-rules-on-linux-servers-by-faruk-ahmed-sep-2025/
Please log in to upload a file.
There are no updates yet.
Click the Upload button above to add an update.