Opposition told ASIO hack 'not successful' The Four Corners report contained "unsubstantiated claims": Prime Minister Julia Gillard. Australian national security officials have denied classified plans of ASIO's new headquarters building were stolen by Chinese hackers and say the opposition was informed of this in a security briefing. According to security officials, there were attempted cyber intrusions against contractors engaged in the ASIO headquarters building project. "This was one of many attempts to obtain sensitive Australian government information, most likely by Chinese intelligence services but there was no compromise," a security official said on condition of anonymity. Contracting firms involved in the project are required to comply with the highest security standards, including in regard to IT security, and this incident demonstrated the effectiveness of those measures. On Monday, the ABC's Four Corners program aired allegations from anonymous informants that Chinese hackers targeted a contracting firm working on the ASIO building and had "stolen the blueprints, not just of the overall building but also of the communications cabling and server locations, of the floor plans, and the security systems." Prime Minister Julia Gillard, Attorney-General Mark Dreyfus and ASIO Director-General David Irvine all refused to comment directly on the allegation in accordance with established national security policy. However in the course of parliamentary debate on national security, Ms Gillard said Four Corners, which canvassed several alleged cyber security breaches, included "unsubstantiated allegations" and "inaccurate reports." Following a classified briefing by ASIO on Tuesday evening, shadow attorney-general George Brandis accused Ms Gillard of making a "false" claim about the Four Corners report. "She dismissed the allegations on the Four Corners program the previous night as being incorrect and inaccurate, and that statement is wrong," he said. Although Senator Brandis' comments were widely interpreted as confirmation of the alleged ASIO security breach, it is understood he and opposition foreign affairs spokeswoman Julie Bishop were told the attempted cyber intrusion against the contractor was unsuccessful and there had been no compromise of the security of the new ASIO headquarters. A spokesperson for Senator Brandis said on Friday he had "nothing to add" to his comments on Wednesday. While emphasising the seriousness of ongoing cyber security threats, government officials suggest the claim may have arisen from "Chinese whispers" among IT security contractors, including former government employees, who were then "keen to beat up security concerns in the interest of building their businesses." An ABC spokesperson said Four Corners "strongly stands by the accuracy of the story but the source is strictly confidential."