SECRET and highly sensitive blueprints outlining the layout of Australia's top spy agency's new headquarters have been stolen by Chinese hackers, the ABC says.

The documents contained details of the ASIO building's floor plans, communication cabling layouts, server locations and security systems, potentially putting the entire organisation at risk, Monday night's Four Corners program alleges. It is unclear precisely when the alleged theft took place, or if there have been diplomatic ramifications from the embarrassing breach. But it comes amid deepening concern about widespread, aggressive state-sponsored hacking by China, with further allegations that its cyber spies have recently obtained sensitive Australian military secrets and foreign affairs documents. Companies including BlueScope Steel and Adelaide-based Codan, which makes radios for military and intelligence agencies, are also said have been targeted by the Chinese, according to the ABC. The allegation comes just weeks after Canberra softened its stance towards China, claiming in May's Defence White Paper that it no longer saw the rising superpower as a threat. Aside from the diplomatic implications, the alleged ASIO theft may help explain why its new headquarters, overlooking Canberra's Lake Burley Griffin, is millions over budget and still not operational. ASIO said in its October annual report that the building would cost taxpayers about $630 million - $41 million more than expected. It was due to open in April, but staff are yet to move in. The ABC did not cite the source of its claims, but said the blueprints had been taken from a contractor involved with the project. "It reeked of an espionage operation. Someone had mounted a cyber hit on a contractor involved in the site," Four Corners reported. "The plans were traced to a server in China." Professor Des Ball, from the Australian National University's Strategic and Defence Studies Centre, suggested the theft meant China could bug the building. "At this stage with construction nearly completed you have two options," he told the ABC. "One is to accept it and practice utmost sensitivity even within your own headquarters. "The other, which the Americans had to do with their new embassy in Washington ... was to rip the whole insides out and to start again." Federal Attorney-General Mark Dreyfus refused to confirm the theft. Whistleblowers interviewed by Four Corners also allege the Australian defence department's classified email and restricted networks have been hacked. "A factor of of ten times the entire database, or the entire amount of information stored within the Defence Restricted Network, has been leached out over a number of years," one worker said. Another whistleblower said a "highly sensitive document" belonging to the Department of Foreign Affairs and Trade had been stolen by China. "It's a project that would give an adversary a significant advantage when dealing with Australia," the source told the ABC about the DFAT document.