Configuring Host Firewalls: UFW and iptables Policy Guidelines

Host firewalls define which network ports can accept incoming traffic, blocking unauthorized access attempts on background interfaces.

1. Uncomplicated Firewall (UFW)

UFW is a user-friendly frontend for iptables on Ubuntu systems:

ufw default deny incoming
ufw default allow outgoing
ufw allow 80/tcp
ufw allow 443/tcp
ufw enable

2. Raw iptables Rules

For advanced packet filtering, you can write iptables policies directly. For example, to block a specific malicious IP address:

iptables -A INPUT -s 192.168.1.99 -j DROP