Flashstart (http://www.flashstart.it) is a web categorization service used to enable network administrators to restrict access to certain traffic categories (e.g. porn, violence, social networks...). To enable the service in ntopng a key is required and has to be specified from the command line using the '--traffic-filtering flashstart:<user>:<pwd>' parameter whose credentials have been received at service signup [1]. [1] http://www.flashstart.it