OPS535 Linux Firewall Review

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