What are east-west and north-south traffic?

North-south traffic flows between your network and the outside world, for example from an office PC to the internet; east-west traffic flows between devices inside your network, for example from a PC to the file server. The firewall at the edge sees north-south traffic but usually not east-west. Once an attacker is inside, most of their work is east-west: scanning, logging in to other machines, copying data to a staging server. That is why internal traffic, seen from a mirror port inside the network, is where lateral movement shows up. NetSenX watches both directions on the segments it monitors.

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