files/ferm.conf


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# -*- shell-script -*-
#
# Ferm example script
#
# Firewall configuration for a workstation which accepts remote ssh login.
#
# Author: Max Kellermann <max@duempel.org>
#

table filter {
    chain INPUT {
        policy DROP;

        # connection tracking
        mod state state INVALID DROP;
        mod state state (ESTABLISHED RELATED) ACCEPT;

        # allow local connections
        interface lo ACCEPT;

        # respond to ping
        proto icmp icmp-type echo-request ACCEPT;

        # allow SSH connections
        proto tcp dport ssh ACCEPT;

        # ident connections are also allowed
        proto tcp dport auth ACCEPT;

        # the rest is dropped by the above policy
    }

    # outgoing connections are not limited
    chain OUTPUT policy ACCEPT;

    # this is not a router
    chain FORWARD policy DROP;
}