OPS535 Linux Firewall Review

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Concepts

  • Netfilter
  • iptables
  • firewall

Command line tools

  • iptables
  • ip6tables
  • arptables
  • ebtables
  • nft

iptables

  • raw table
    • PREROUTING chain
    • OUTPUT chain
  • managle table
    • PREROUTING
    • INPUT
    • FORWARD
    • OUTPUT
    • POSTROUTING
  • nat table
    • PREROUTING
    • INPUT
    • OUTPUT
    • POSTROUTING
  • filter table
    • INPUT
    • FORWARD
    • OUTPUT
  • security table
    • INPUT
    • FORWARD
    • OUTPUT

rules

iptables -t filter -A INPUT -p tcp --dport 22 -j ACCEPT
          |---------------| |---------------| |--------|
           where and when     match spec.       action