Data from firewalls and from intrusion detection systems analyze network traffic and being capable of visualizing them could provide a large insight to cyber security. One possibilty is to use a directional graph-like structure where arrows are used to indicate the direction of traffic between nodes, identifying the source and destination of connections. Color could also be used to identify more information regarding the nodes, such as address range or local servers. Of course such a visualization would become quite unreadable if analyzing a very large amount of nodes, as they would most likely start to overlap other elements of the graph.
[Conti, Greg, Security Data Visualization, Graphical Techniques for Network Analysis. pp. 127-130]