AIX must employ a deny-all, allow-by-exception firewall policy for allowing connections to other systems.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-219057	SRG-OS-000480-GPOS-00227	AIX7-00-003143	SV-219057r991589_rule	2024-08-16	3

Description
Failure to restrict network connectivity only to authorized systems permits inbound connections from malicious systems. It also permits outbound connections that may facilitate exfiltration of DoD data.

ℹ️ Check
From the command prompt, run the following commands to check if the "all traffic" filter rules, the predefined rule with Rule-ID 0, are defined to deny all packages: # lsfilt -v4 -n0 # lsfilt -v6 -n0 Rule 0: Rule action : deny Source Address : 0.0.0.0 Source Mask : 0.0.0.0 Destination Address : 0.0.0.0 Destination Mask : 0.0.0.0 Source Routing : yes Protocol : all Source Port : any 0 Destination Port : any 0 Scope : both Direction : both Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : no Expiration Time : 0 Description : Default Rule Rule 0: Rule action : deny Source Address : :: Source Mask : 0 Destination Address : :: Destination Mask : 0 Source Routing : yes Protocol : all Source Port : any 0 Destination Port : any 0 Scope : both Direction : both Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : no Expiration Time : 0 Description : Default Rule If any of the "all traffic" rules has "Rule action : permit", this is a finding.

ℹ️ Check

From the command prompt, run the following commands to check if the "all traffic" filter rules, the predefined rule with Rule-ID 0, are defined to deny all packages: # lsfilt -v4 -n0 # lsfilt -v6 -n0 Rule 0: Rule action : deny Source Address : 0.0.0.0 Source Mask : 0.0.0.0 Destination Address : 0.0.0.0 Destination Mask : 0.0.0.0 Source Routing : yes Protocol : all Source Port : any 0 Destination Port : any 0 Scope : both Direction : both Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : no Expiration Time : 0 Description : Default Rule Rule 0: Rule action : deny Source Address : :: Source Mask : 0 Destination Address : :: Destination Mask : 0 Source Routing : yes Protocol : all Source Port : any 0 Destination Port : any 0 Scope : both Direction : both Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : no Expiration Time : 0 Description : Default Rule If any of the "all traffic" rules has "Rule action : permit", this is a finding.

✔️ Fix
From the command prompt, run the following commands to create and activate "ipsec_v4" and "ipsec_v6" devices: # mkdev -l ipsec -t 4 # mkdev -l ipsec -t 6 From the command prompt, run the following commands to change the "all traffic" rules to block all packages: # chfilt -a D -v 4 -n 0 # chfilt -a D -v 6 -n 0 Assume that the local host has IP address 10.10.10.10 and the remote host has IP address 11.11.11.11, run the following command to generate a user-defined filter rule that allow all IPv4 traffic between these 2 hosts: # genfilt -w B -v 4 -s 10.10.10.10 -p 0 -P 0 -o any -O any -m 255.255.255.255 -M 255.255.255.255 -i all -g Y -d 11.11.11.11 -c all -a P From the command prompt, run the following command to activate all the filter rules in the rule database: # mkfilt -u

✔️ Fix

From the command prompt, run the following commands to create and activate "ipsec_v4" and "ipsec_v6" devices: # mkdev -l ipsec -t 4 # mkdev -l ipsec -t 6 From the command prompt, run the following commands to change the "all traffic" rules to block all packages: # chfilt -a D -v 4 -n 0 # chfilt -a D -v 6 -n 0 Assume that the local host has IP address 10.10.10.10 and the remote host has IP address 11.11.11.11, run the following command to generate a user-defined filter rule that allow all IPv4 traffic between these 2 hosts: # genfilt -w B -v 4 -s 10.10.10.10 -p 0 -P 0 -o any -O any -m 255.255.255.255 -M 255.255.255.255 -i all -g Y -d 11.11.11.11 -c all -a P From the command prompt, run the following command to activate all the filter rules in the rule database: # mkfilt -u