UFW vs IPTables: Rule Simplicity and Firewall Performance Compared

The Netfilter Ecosystem on Linux

Linux packet filtering takes place inside the kernel netfilter subsystem. However, managing raw iptables or nftables syntax can be intimidating. Ubuntu introduced ufw to provide human-readable command syntax.

Syntax Comparison

Notice the clarity advantage of UFW when allowing SSH from a specific subnet:

# UFW Syntax
sudo ufw allow from 192.168.1.0/24 to any port 22 proto tcp

# Equivalent raw iptables syntax
sudo iptables -A INPUT -p tcp -s 192.168.1.0/24 --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

The Docker Caveat

The primary hazard when using UFW on modern dev servers is Docker. When you publish a container port (e.g. -p 8080:8080), Docker inserts raw rules into the iptables DOCKER chain before UFW's rules are evaluated, exposing the port even if UFW has default deny enabled. To resolve this, administrative rules should be anchored to the DOCKER-USER chain.

Conclusion

For standalone virtual servers and small engineering teams, UFW drastically reduces firewall misconfiguration risk. For complex cloud gateways with NAT routing and custom chains, raw iptables/nftables remains necessary.