iptables

Linux kernel packet filtering and NAT administration tool

brewmacoslinux

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Linux kernel packet control tool

iptablesiptables-saveiptables-restoreiptables-xml

List all firewall rules in the filter table$ iptables -L -n -v

Block incoming traffic from a specific IP address$ iptables -A INPUT -s 192.168.1.100 -j DROP

Allow incoming SSH connections on port 22$ iptables -A INPUT -p tcp --dport 22 -j ACCEPT