One or more terminals that are coupled to a packet-based network are installed with a first instance and/or a second instance of a communication client application of a first user. At times, the communication client application can be configured to enable the first user to communicate with other users using a first communication system implemented over the packet-based network. In some cases, a controller coupled to the packet-based network can be used to maintain separate privacy settings for each of the first and second instances, and thereby control the privacy of the first user in relation to the other users within the first communication system in dependence on which of the first and second instances is active.