Abstract: This disclosure describes systems, devices, and techniques for implementing master rules in firewalls. In some cases, at least one master rule is identified. The at least one master rule can be associated with performing at least one first operation on a first type of data traffic that satisfies at least one first condition. Multiple firewalls may implement the at least one master rule. In addition, a first firewall among the multiple firewalls may implement at least one application-specific rule in addition to the at least one master rule. The at least one application-specific rule may be associated with performing at least one second operation on a second type of data traffic that satisfies at least one second condition. The multiple firewalls may be between multiple applications and at least one network. Specifically, the first firewall may be deployed between a first application among the multiple applications and the network(s).