The systems local IPv4 firewall must implement a deny-all, allow-by-exception policy for inbound packets.

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The systems local IPv4 firewall must implement a deny-all, allow-by-exception policy for inbound packets.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-38513	RHEL-06-000120	SV-50314r2_rule		Medium

Description
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.

STIG	Date
Red Hat Enterprise Linux 6 Security Technical Implementation Guide	2020-05-19

Details

Check Text ( C-46070r2_chk )
Run the following command to ensure the default "INPUT" policy is "DROP": # iptables -nvL \| grep -i input Chain INPUT (policy DROP 0 packets, 0 bytes) If the default policy for the INPUT chain is not set to DROP, this is a finding.

Fix Text (F-43460r1_fix)
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]