FreeBSD 8 (Generic ядро)
echo 'firewall_enable="YES"' >>/etc/rc.conf
echo 'firewall_type="open"' >>/etc/rc.conf
echo 'ipfw add 10 deny icmp from any to any' >> /etc/rc.firewall
и перезагрузить OS - shutdown -r now
Linux (Centos / Debian)
echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all
echo 'icmp_echo_ignore_all = 1
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px Helvetica}
