参考博客：ICMP timestamp请求响应漏洞处理(CVE-1999-0524)

Iptables

vi /etc/sysconfig/iptables
-A INPUT -p icmp -m icmp --icmp-type timestamp-request -j DROP
-A OUTPUT -p icmp -m icmp --icmp-type timestamp-reply -j DROP

重启防火墙

service iptables restart

Firewalld

添加防火墙规则

firewall-cmd --permanent --zone=public --add-icmp-block=timestamp-reply
firewall-cmd --permanent --zone=public --add-icmp-block=timestamp-request
firewall-cmd --reload