A network activity visualization system can include a minimum description length (MDL) based network intrusion detection system having an MDL grammar database adapted to store a plurality of MDL grammars, and a pattern matching module adapted to match a received network activity data set against the MDL grammars by calculating a distance of the network activity data set from each MDL grammar. The system can also include an intelligent icon module coupled to the MDL-based intrusion detection system and adapted to receive the MDL grammars and distances of a network data set from each respective MDL grammar, and adapted to generate intelligent icons based on the MDL grammars and distances. The system can further include a display system adapted to display the intelligent icons so as to provide a visual indication of network security.