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


Finding ID Version Rule ID IA Controls Severity
V-218060 RHEL-06-000320 SV-218060r505923_rule Medium
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.
Red Hat Enterprise Linux 6 Security Technical Implementation Guide 2020-09-03


Check Text ( C-19541r377195_chk )
Run the following command to ensure the default "FORWARD" policy is "DROP":

# iptables -nvL | grep -i forward

Chain FORWARD (policy DROP 0 packets, 0 bytes)

If the default policy for the FORWARD chain is not set to DROP, this is a finding.
Fix Text (F-19539r377196_fix)
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":