Methods and systems for determining and collecting information about channels being displayed on a display device are described. Such methods and systems provide an effective way for entities to collect reliable and detailed viewership information. Conditional access modules are associated with panelists who are part of a viewership measurement program. A conditional access module is also associated with a display device, and sends messages to a server. The messages include data that can be used to identify the channel to which the display device is tuned. The server collects and compiles data about a group of TV channels. The server determines a match between the stored data and the received message to determine what TV channel is being displayed at the display device.