eSTOP! was developed as a security product with the intent to view and (e)mergency STOP problem TCP connections. It displays in real-time any TCP connection in or out of your computer. Web connections are an example of a TCP connection. You can instantly stop that connection by double clicking on the connection in the list or by pressing one of the three large red buttons on the main window. Now with logging and blocking by port, IP address, hostname or domain name.
eSTOP! is not a firewall. eSTOP! complements a firewall because you can use it to stop connections normally permitted by the firewall. You can make eSTOP! popup whenever connections happen--then do something about those connections!