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Running a server

Protect a server with a firewall (CSF)

Install ConfigServer Firewall, and the settings that matter on the first day.

1 min read Updated

A server you rent is yours to secure. ConfigServer Firewall (CSF) is the usual first step on a Linux server: it controls which ports are reachable and, through its login-failure daemon, blocks addresses that keep guessing passwords.

These steps assume you are connected over SSH as root.

Install it

bash
cd /usr/local/src
wget https://download.configserver.com/csf.tgz
tar -xzf csf.tgz
cd csf

Then run the installer that matches the server:

bash
./install.cpanel.sh      # a server running cPanel/WHM
./install.directadmin.sh # a server running DirectAdmin
./install.generic.sh     # a server with no hosting panel

CSF installs into /etc/csf and picks up the ports currently in use.

Before you walk away

  1. Open /etc/csf/csf.conf and check that your SSH port is in TCP_IN. Locking yourself out is the classic first mistake.
  2. Restart the firewall so the rules apply:

    ``bash csf -r ``

  3. When you are sure you can still connect, take it out of testing mode: set TESTING = "0" in /etc/csf/csf.conf and restart again. While TESTING is 1, the rules are flushed every few minutes and protect nothing.

Important

Keep the server's management panel to hand while you work — it is how you get back in if a rule shuts you out. See Access your VPS or dedicated server.

Useful commands

bash
csf -a 203.0.113.10   # allow an address
csf -d 203.0.113.10   # block an address
csf -g 203.0.113.10   # see why an address is blocked
csf -tf               # clear all temporary blocks

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