A method and system for detecting network reconnaissance is disclosed wherein network traffic can be parsed into unidirectional flows that correspond to sessions. A learning module may categorize computing entities inside the network into assets and generate asset data to monitor the computing entities. If one or more computing entities address a flow to an address of a host that no longer exists, ghost asset data may be recorded and updated in the asset data. When a computing entity inside the network contacts an object in the dark-net, the computing entity may be recorded a potential mapper. When the computing entity tries to contact a number of objects in the dark-net, such that a computed threshold is exceeded, the computing entity is identified a malicious entity performing network reconnaissance.