Chinese military unit accused of cyber attacks on 141 companies
The report claimed to have uncovered evidence connecting the so-called APT1 cyber espionage campaign to secretive branch of China's military, codenamed Unit 61398.
"Our analysis has led us to conclude that APT1 is likely government-sponsored and one of the most persistent of China's cyber threat actors," reads the report.
"We believe that APT1 is able to wage such a long-running and extensive cyber espionage campaign in large part because it receives direct government support."
Mandiant added that its investigation of AP1 is not finished, but that current evidence suggests the hacking group could have stolen hundreds of terabytes of data from over 140 organisations across the world.
The New York Times has since identified Unit 61398 as the Comment Crew, a hacker team the US currently believes is responsible for attacks on a number of businesses connected to the country's critical infrastructure.
APT1 is one of 20 advanced cyber campaigns being tracked by Mandiant.
At the time of publishing neither the US nor Chinese London embassies had responded to V3's request for comment on the report.
The report is the latest in a long line of tit-for-tat hacking allegations between the Chinese and US governments.
Earlier this year the New York Times and the Wall Street Journal issued reports claiming they were the victims of a malicious series of cyber attacks stemming from China.
The two publications both accused Chinese hackers of mounting the attacks as "payback" for a series of articles the paper published about Chinese prime minister Wen Jiabao.
In the past US authorities have warned that Chinese firms such as ZTE and Huawei could be influenced by the government to infiltrate networks in the West - allegations both firms strenously deny.
"Huawei and ZTE provide a wealth of opportunities for Chinese intelligence agencies to insert malicious hardware or software implants into critical telecommunications components and systems," read the US report last October.
"It appears under Chinese law, ZTE and Huawei would likely be required to co-operate with any request by the Chinese government to use their systems or access for malicious purposes."
However, other reports by the US have admitted they found no evidence of any wrong doing by Huawei. All the incidents underline the growing tensions between the US and China, despite leaders in both nations claiming this is not the case.