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Jednoduchý Linux firewall

iptables -F
iptables -X
iptables -Z
 
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT
 
iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p icmp --icmp-type 3 -j ACCEPT
iptables -A INPUT -p icmp --icmp-type 11 -j ACCEPT
iptables -A INPUT -p icmp --icmp-type 12 -j ACCEPT
iptables -A INPUT -p tcp --syn --dport 113 -j REJECT --reject-with tcp-reset