I am setting up firewall with iptables on my host. I want to disable timestamp ICMP request, but it's wired, I only allows type 8 (echo-request) comes into host, but event still, I can get timestamp from my host
64 bytes from xxxxxxxxx: icmp_seq=2 ttl=61 time=2.56 ms TS: 36654775 absolute -6423 3 1 -4 0 4 0 -2 Unrecorded hops: 1
I try to allow type 8 only, but it doesn't work, it appears that all I can do is to let all ICMP requests pass, or deny all of them, following is the configuration script I'm using.
iptables -F iptables -X iptables -Z iptables -P INPUT DROP iptables -P OUTPUT ACCEPT iptables -P FORWARD ACCEPT iptables -A INPUT -i lo -j ACCEPT iptables -A INPUT -m state --state RELATED -j ACCEPT # allow the icmp iptables -I INPUT -p icmp --icmp-type 8 -j ACCEPT # services iptables -A INPUT -p TCP --dport 22 -j ACCEPT # SSH iptables -A INPUT -p UDP --sport 53 -j ACCEPT # DNS iptables -A INPUT -p TCP --sport 53 -j ACCEPT # DNS iptables -A INPUT -p TCP --dport 80 -j ACCEPT # HTTP iptables -A INPUT -p TCP --dport 443 -j ACCEPT # HTTPS # allow the replay from outgoing established connection iptables -A INPUT -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT
The version of Linux kernel is 2.6.18, and the version of iptables is v1.3.5. What's wrong with that? How to block time stamp requests?