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-50987	OL6-00-000120	SV-65193r1_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
Oracle Linux 6 Security Technical Implementation Guide	2019-03-20

Details

Check Text ( C-53429r1_chk )
Inspect the file "/etc/sysconfig/iptables" to determine the default policy for the INPUT chain. It should be set to DROP. # grep ":INPUT" /etc/sysconfig/iptables If the default policy for the INPUT chain is not set to DROP, this is a finding.

Fix Text (F-55789r1_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]