COMPUTER NETWORK SECURITY SYSTEM

A computer network security system includes a central controller in communication with software-based endpoint agents operating on individual host computers. The endpoint agents monitor new connection requests to and from their respective hosts, comparing the connections to cached rules obtained from the controller, and holding new connections while escalating requests for applicable rules and/or directives to the controller in real-time when no applicable rules are available in their caches. The endpoint agents can be configured to present a pop-up dialog requesting enhanced authentication credentials from a user on a host in response to a connection request from a restricted network-based application. The pop-up dialog enables enhanced or two-factor authentication functionality to be overlaid on any networked application regardless of the application's inherent authentication capability.