A Chinese military unit appeared to be a major hacker of US computer systems in a "multi-year, enterprise-scale computer espionage campaign," US-based cybersecurity experts said in a report issued Tuesday, DPA reported.
The Mandiant Intelligence Centre published 3,000 digital indicators of activity by the Chinese unit, which it called APT1, including domain names and IP addresses linked to hacking attacks.
"APT1 is one of dozens of threat groups Mandiant tracks around the world, and we consider it to be one of the most prolific in terms of the sheer quantity of information it has stolen," Mandiant said.
The hackers appeared to be linked to the Shanghai-based Unit 61398 of the People's Liberation Army, it said.
In Washington, the White House said it was aware of the reports but would not discuss intelligence assessments or the specific allegation. Spokesman Jay Carney did point to recently announced efforts by President Barack Obama to bolster cybersecurity and noted the United States had "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."
"This is a very important challenge. It is one the president has been working on and urging Congress to take action on for quite some time, and he'll continue to do that," Carney said.
"The United States and China are among the world's largest cyber actors, and it is vital that we continue a sustained, meaningful dialogue and work together to develop an understanding of acceptable behavior in cyberspace."
The report coincided with a statement from Apple that it had been infiltrated in the same sort of attack that Facebook acknowledged last week, which security experts had linked to China.
"It is time to acknowledge the threat is originating from China, and we wanted to do our part to arm and prepare security professionals to combat the threat effectively," Mandiant said of its decision to publicize its findings.
"The issue of attribution has always been a missing link in the public's understanding of the landscape of APT (advanced persistent threat) cyberespionage. Without establishing a solid connection to China, there will always be room for observers to dismiss APT actions as uncoordinated, solely criminal in nature, or peripheral to larger national security and global economic concerns."
US security experts said that the report illustrated the grave dangers facing the country's basic infrastructure such as its water supply, oil pipelines and financial systems.
"I call it cyberterrorism that makes 9/11 pale in comparison," Congressman Mike Rogers, a Michigan Republican and chair of the House Intelligence Committee, told NBC News on Tuesday.
China's Foreign Ministry rejected the allegations in the report as "groundless."
"Groundless criticism is irresponsible and unprofessional, and it will not help to solve the problem," ministry spokesman Hong Lei said when asked about Mandiant's report.
Hong said China was committed to fighting cybercrime and was a "major victim" of hacking attacks.
Chinese government experts found 73,000 foreign IP addresses that were linked to attacks on 14 million computers in China, with the largest number of attacks originating in the United States, he said.
Apple said the issue affected only a small number of computers and that there was no evidence that consumer data had been compromised.
Apple's description of the attack appeared to match methods used by hackers to infiltrate Facebook by using a so-called zero-day exploit of the Java plug-in to infect users of a site visited by software developers.
"The malware was employed in an attack against Apple and other companies and was spread through a website for software developers," Apple said.
State Department spokeswoman Victoria Nuland said Tuesday that the US has "substantial and growing" concerns about threats to its economy and national security posed by cyber attacks.
"I think as recent public reports make clear, we're obviously going to have to keep working on this," she said. "It's a serious concern."