Completely remove nf_conntrack from kernel

1. Remove the following line, if it exists, in /etc/sysconfig/iptables-config
   IPTABLES_MODULES="ip_conntrack_netbios_ns"

2. Stop iptables
   iptables -F

3. Remove the related modules
   modprobe -r xt_NOTRACK nf_conntrack_netbios_ns nf_conntrack_ipv4 xt_state
   modprobe -r iptable_nat ipt_MASQUERADE nf_nat nf_defrag_ipv4
   modprobe -r nf_conntrack

nf_conntrack: table full, dropping packet.

Could be DoS/DDoS attack

echo 102400 > /proc/sys/net/netfilter/nf_conntrack_max
echo 120 > /proc/sys/net/netfilter/nf_conntrack_generic_timeout
echo 54000 > /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_established
echo 30 > /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_time_wait
sysctl -p