A firewall provides improved network security by allowing the use of dynamic objects in firewall rules, where the dynamic objects evaluate to a variable set of devices. The dynamic objects may be updated from real-time data sources and non-real time inventories of data. Dynamic objects may be used for either or both of source and destination in a firewall rule. Where the dynamic object includes non-real time data, the dynamic object may be synchronized with the non-real time data inventory on a configurable basis. By using dynamic objects, the firewall can provide flexibility in the rules to allow control over user-owned and controlled devices.