Close ports on Linode Debian

  • Hello all,

    I have been trying to figure out what firewall I have on our Debian host but cannot. I did a port scan and found that we have some ports open that I want to close as I know we don't use any of them.

  • Use UFW

    apt-get install -y ufw

    Then open only what you need to use. Here are examples.

    ufw enable
    ufw allow in ssh
    ufw allow in http
    ufw allow in https
    ufw allow in 10000:20000/udp

  • FYI, this writes to iptables for you as far as I know.

  • Beyond using a firewall, you can also set whatever ports to simply not be open. Firewalls block ports, but leave them open. You can close them additionally. Your best defense is doing both.

  • By default Debian comes with iptables. It will allowing everything but a normal Debian install have no services running.

    Run iptables -L to see the firewall rules.

    On Debian 10 the default is nftables.

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