Set Default iptables Policy for Forwarded Packets
An XCCDF Rule
Description
To set the default policy to DROP (instead of ACCEPT) for
the built-in FORWARD chain which processes packets that will be forwarded from
one interface to another,
add or correct the following line in
/etc/sysconfig/iptables:
:FORWARD DROP [0:0]
Rationale
In iptables, the default policy is applied only after all
the applicable rules in the table are examined for a match. Setting the
default policy to DROP implements proper design for a firewall, i.e.
any packets which are not explicitly permitted should not be
accepted.
- ID
- xccdf_org.ssgproject.content_rule_set_iptables_default_rule_forward
- Severity
- Medium
- References
- Updated
Remediation - Shell Script
# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q installed; then
sed -i 's/^:FORWARD ACCEPT.*/:FORWARD DROP [0:0]/g' /etc/sysconfig/iptables
else