AIX must not process ICMP timestamp requests.

The processing of Internet Control Message Protocol (ICMP) timestamp requests increases the attack surface of the system.

From the command prompt, run the following command to check if "ipsec_v4" and "ipsec_v6" devices are active: # lsdev -Cc ipsec The above command should yield the following output: ipsec_v4 Available IP Version 4 Security Extension ipsec_v6 Available IP Version 6 Security Extension If "ipsec_v4" or "ipsec_v6" is not displayed, or it is not in "Available" state, this is a finding. Determine if the system is configured to respond to ICMP Timestamp requests using the following command: # lsfilt Beginning of IPv4 filter rules. Rule 1: Rule action : permit 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 : no Protocol : udp Source Port : eq 4001 Destination Port : eq 4001 Scope : both Direction : both Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : yes Expiration Time : 0 Description : Default Rule Rule 2: *** Dynamic filter placement rule for IKE tunnels *** Logging control : no Rule 3: 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 : icmp ICMP type : any 0 ICMP code : eq 13 Scope : both Direction : inbound Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : no Expiration Time : 0 Description : Rule 4: 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 : icmp ICMP type : eq 14 ICMP code : any 0 Scope : both Direction : outbound Logging control : no Fragment control : all packets Tunnel ID number : 0 Interface : all Auto-Generated : no Expiration Time : 0 Description : Rule 0: Rule action : permit 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 End of IPv4 filter rules. If there is no rule blocking ICMP packet type of "13" and ICMP packet type of "14" (rule #3 and rule #4 above), this is a finding.

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 Run the following commands to create 2 IPsec rules to block the ICMP timestamp request and reply: # genfilt -v 4 -a D -s 0 -m 0 -d 0 -M 0 -c icmp -O eq -P 13 -r B -w I -i all # genfilt -v 4 -a D -s 0 -m 0 -d 0 -M 0 -c icmp -o eq -p 14 -r B -w O -i all From the command prompt, run the following command to activate all the filter rules in the rule database: # mkfilt -u