Information
A default deny policy on connections ensures that any unconfigured network usage will be rejected.
Rationale:
With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to white list acceptable usage than to black list unacceptable usage.
Solution
Run the following commands to implement a default deny policy:
# ufw default deny incoming
# ufw default deny outgoing
# ufw default deny routed