Methods, apparatus, and articles of manufacture to provide firewalls for process control systems are disclosed. An example method includes analyzing a network communication to identify a first service, an address associated with the first service within a secured portion of a network, and a subset of ports used by the first service, the network communication originating from within the secured portion of the network and to be transmitted to a destination outside of the secured portion of the network, and storing an identifier of the first service, the address, and the subset of the ports when the network communication includes the identifier, the address, and the subset of the ports.