Set Default iptables Policy for Incoming Packets
An XCCDF Rule
Description
To set the default policy to DROP (instead of ACCEPT) for
the built-in INPUT chain which processes incoming packets,
add or correct the following line in
/etc/sysconfig/iptables:
:INPUT 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
- Severity
- Medium
- References
- Updated
Remediation - Shell Script
# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q installed && { ( ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q installed ) && ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q installed ) ); }; then
sed -i 's/^:INPUT ACCEPT.*/:INPUT DROP [0:0]/g' /etc/sysconfig/iptables
else