DigitalOcean Cloud Firewalls are a network-based, stateful firewall service for Droplets provided at no additional cost. Cloud firewalls block all traffic that isn’t expressly permitted by a rule.
Firewalls place a barrier between your servers and other machines on the network to protect them from external attacks. Firewalls can be host-based, which are configured on a per-server basis using services like IPTables or UFW. Others, like DigitalOcean Cloud Firewalls, are network-based and stop traffic at the network layer before it reaches the server.