Methods, computer program products, and systems are presented. The method computer program products, and systems can include, for instance: examining data of breaches of a geofence by client computer devices to determine respective positions of the breaches; establishing an updated location for the geofence using the determined respective positions of the breaches; updating a location of the geofence so that the location of the geofence is the updated location; obtaining data of a client computer breach of the geofence at the updated location; and providing one or more output in response to the obtaining data of a client computer breach of the geofence at the updated location.