Table of Contents

ICMP Timestamp
- Iptable
  - Check
- Firewall-cmd

ICMP Timestamp

To fix “ICMP Timestamp Reply Information Disclosure”“

Iptable

iptables -A INPUT -p icmp --icmp-type timestamp-request -j DROP
iptables -A OUTPUT -p icmp --icmp-type timestamp-reply -j DROP

Check

iptables -L | grep timestamp

DROP       icmp --  anywhere             anywhere             icmp timestamp-request
DROP       icmp --  anywhere             anywhere             icmp timestamp-reply

Firewall-cmd

 firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT -5 -p icmp --icmp-type timestamp-request -j DROP

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