The system must not process Internet Control Message Protocol (ICMP) timestamp requests.

From SUSE Linux Enterprise Server v11 for System z

Associated with: CCI-001551

SV-45721r1_rule The system must not process Internet Control Message Protocol (ICMP) timestamp requests.

Vulnerability discussion

The processing of (ICMP) timestamp requests increases the attack surface of the system.

Check content

Verify the system does not respond to ICMP TIMESTAMP_REQUESTs Procedure: # iptables -L INPUT | grep "timestamp" This should return the following entries for "timestamp-reply" and "timestamp_request": DROP icmp -- anywhere anywhere icmp timestamp-request DROP icmp -- anywhere anywhere icmp timestamp-reply If either does not exist or does not "DROP" the message, this is a finding.

Fix text

Configure the system to not respond to ICMP TIMESTAMP_REQUESTs. This is done by rejecting ICMP type 13 and 14 messages at the firewall. Procedure: 1. Check the SuSEfirewall2 configuration to see if custom rules are being used: # grep -v '^#' /etc/sysconfig/SuSEfirewall2 | grep FW_CUSTOMRULES If the command returns FW_CUSTOMRULES=”” then no custom rules are being used. In that case edit the /etc/sysconfig/SuSEfirewall2 file and use the vendor supplied file by setting FW_CUSTOMRULES="/etc/sysconfig/scripts/SuSEfirewall2-custom" 2. Edit the file defined by the FW_CUSTOMRULES variable and add these commands to append the INPUT chain: iptables -A INPUT -p ICMP --icmp-type timestamp-request -j DROP iptables -A INPUT -p ICMP --icmp-type timestamp-reply -j DROP Restart the firewall: # rcSuSEfirewall2 restart

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