US: China hacking 'repeatedly raised at highest level' 20 February 2013 Last updated at 06:32 The BBC's John Sudworth was detained while filming the reported hub of the hacking operation The US says it has repeatedly raised concerns with Beijing about cyber theft, as a report linked a hacking group with a Chinese military unit. While not commenting directly on the report, a White House spokesman called cyber theft a "major challenge" in the national security arena. The report identified a Shanghai high-rise used by the military as the likely home of a prolific hacking group. China's Defence Ministry has denied any role in hacking. In a statement posted on its website on Wednesday, it called the claims scientifically flawed and unreliable. The scale of the Chinese hacking alleged by the computer security firm Mandiant is striking. Until now the bulk of this hacking has been a digital version of old-fashioned industrial espionage - stealing designs and company secrets. But there is a more sinister side to this activity as well. Chinese hackers are alleged to have a growing interest in gaining access to key parts of the US infrastructure - gas lines, power grids and waterworks. President Barack Obama himself warned during his recent State of the Union address that the nature of the cyber threat was changing. Gaining access to critical systems is the key. Once inside the digital perimeter - especially if the intrusion is not identified, there is the possibility of causing real physical damage to the infrastructure that the computers control. "The report, in only relying on linking IP address to reach a conclusion the hacking attacks originated from China, lacks technical proof," it said, adding many hacking attacks were carried out using stolen IP addresses. The statement went on to say that there was no clear definition of what constituted a hacking attack and as it was a cross-border, deceptive business, it was hard to pin down where attacks originated. Cyber espionage The detailed report, by US-based computer security company Mandiant, looked at hundreds of data breaches, most of which it attributed to what it termed "Advanced Persistent Threat" actors. The details it had uncovered, it said, showed that these groups were based primarily in China and that the Beijing government was aware of them. The most prolific of these actors was APT1, Mandiant said, describing it as "one of the most prolific cyber espionage groups in terms of the sheer quantity of information stolen." The firm said it had traced the hacking activities of APT1 to a Shanghai building. Unit 61398 of the People's Liberation Army "is also located in precisely the same area" and the actors had similar "missions, capabilities and resources," it added. APT1, it said, was staffed by hundreds of proficient English speakers. It had hacked into 141 companies across 20 industries, stealing information including blueprints, business plans, pricing documents, user credentials, emails and contact lists. Spokesman Jay Carney said the White House was "aware" of the Mandiant report and its contents. While not commenting directly, he described cyber espionage as a "very important challenge." "We have repeatedly raised our concerns at the highest levels about cyber-theft with senior Chinese officials including in the military and we will continue to do so," he said. State Department spokeswoman Victoria Nuland, meanwhile, said that the issue came up ""in virtually every meeting we have with Chinese officials." "We consider this kind of activity a threat not only to our national security but also to our economic interests and [we are] laying out our concerns specifically so that we can see if there's a path forward," she said. China has long been suspected of a role in cyber hacking. But the issue has become more high-profile in recent months following widely reported hacks into media outlets including the New York Times - in that case apparently linked to a report on the wealth of relatives of outgoing Premier Wen Jiabao. A Global Times editorial accused the US and its major allies of hyping up a China hacking "threat." "China should refute the allegations of US company Mandiant with authoritative reports from its technology sector," it said. As a long-term counter-measure, China needs to encourage those institutions and individuals who have been subject to cyber-attacks from US IP addresses to stand up and tell the world what happened to them.