====== ICMP Timestamp ======
To fix "ICMP Timestamp Reply Information Disclosure""

===== Iptable =====

<code bash>
iptables -A INPUT -p icmp --icmp-type timestamp-request -j DROP
iptables -A OUTPUT -p icmp --icmp-type timestamp-reply -j DROP
</code>
==== Check ====
<code bash>iptables -L | grep timestamp</code>
<code>
DROP       icmp --  anywhere             anywhere             icmp timestamp-request
DROP       icmp --  anywhere             anywhere             icmp timestamp-reply
</code>

===== Firewall-cmd =====
<code bash> firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT -5 -p icmp --icmp-type timestamp-request -j DROP</code>

Reference: https://www.golinuxcloud.com/disable-icmp-timestamp-responses-in-linux/