This is Selection Agents window. Every line at the right of the icon represents an agent: the user can select any number of agents and sniff them by typing ALT+S or selecting Do Sniff This Agent(s) from the Actions menu. To unsniff the agents the user must select them then type ALT+N or select Do Not Sniff This Agent(s) from the Actions menu. To add or remove an agent from the canvas without sniffing - unsniffing it the user has only to double-click on the name.