Secret spy station on Cocos Islands Never publicly acknowledged: The Cocos Island facility. Australia's electronic spy agency is intercepting Indonesian naval and military communications through a secret radio listening post on the remote Cocos Islands. According to former defence officials, the Defence Signals Directorate operates the signals interception and monitoring facility - known locally as "the house with no windows" - on Australia's Indian Ocean territory, 1100 kilometres south-west of Java. The station has never been publicly acknowledged. The station has never been publicly acknowledged by the Australian government, or reported in the media, despite being in operation for more than two decades. Along with the better-known Shoal Bay Receiving Station near Darwin, the previously unreported Cocos Island facility forms a crucial part of Australia's signals intelligence collection efforts targeting Indonesia. The facility includes radio-monitoring and direction-finding equipment, and a satellite ground station. The Defence Department would not comment on the facility and said only that the Cocos Islands host "a communications station" that "forms part of the wider Defence communications network." However, former Defence officers have confirmed the station is a Defence Signals Directorate facility devoted to maritime and military surveillance, especially Indonesian naval, air force and military communications. Australian National University intelligence expert Professor Des Ball said the facility was operated remotely from DSD headquarters at Russell Hill in Canberra. Intercepted signals are encrypted and relayed to Canberra. He said preparations to establish the Cocos facility began in the late 1980s, and involved a highly secretive signals intelligence group, the Royal Australian Air Force's No. 3 Telecommunications Unit. The Cocos Islands signals intelligence station forms part of much broader Australian espionage efforts directed against Indonesia. As reported by Fairfax Media on Thursday, these programs include a covert DSD surveillance facility located at the Australian Embassy in Jakarta. A former Defence intelligence officer said Australia's monitoring of Indonesian communications was "very effective" and also allowed assessments of the seriousness of Indonesian efforts to combat people smuggling, which were described as "woeful, wilfully so." However, the former intelligence officer said the Cocos and Shoal Bay facilities were of "limited utility" in locating vessels carrying asylum seekers, which avoided using radios or satellite phones until the vessels contacted the Australian Maritime Safety Authority. Professor Richard Tanter of the Nautilus Institute of Security and Sustainability said the Cocos station was likely to intercept increasing volumes of naval and military communications. With the increasing Australian and US interest in the Indian Ocean region and the planned maritime surveillance deployments, it is likely to become more important. Indonesia announced this week that it was prepared to step up naval patrols between Java and Australia to help combat people smuggling. In anticipation of talks with Immigration Minister Scott Morrison, an Indonesian government spokesman said Indonesia would offer to "maximise our navy patrols in the south sea . . . because these asylum seekers are trying to go south."