Cyber security agencies in the UK and US have played down claims that the China military inserted spy chips into computer hardware before it was exported abroad.
Apple and Amazon, the largest two companies which were connected to the allegedly affected supplier Super Micro, issued strong denials in response to the report last week.
The department of homeland security in the US said it was "aware of the media reports of a technology supply chain compromise" which alleged that dozens of firms had been compromised by the secret spy chip inserted during the manufacturing process.
Amazon was the first company to discover the rice grain-sized chip according to the lengthy report in Bloomberg, which would allow Chinese military hackers access to computer networks in secret.
The report claimed that in addition to Apple and Amazon, Super Micro manufactured equipment for the US defence department's data centres and other federal government functions – some operated by Apple and Amazon Web Services.
Apple and Amazon both denied the claims.
Apple said in a statement it had "never found malicious chips, 'hardware manipulations' or vulnerabilities purposely planted in any server".
Amazon responded that "at no time, past or present, have we ever found any issues relating to modified hardware or malicious chips in Super Micro motherboards in any Elemental or Amazon systems".
In a statement, the DHS said: "Like our partners in the UK, the National Cyber Security Centre, at this time we have no reason to doubt the statements from the companies named in the story.
"Information and communications technology supply chain security is core to DHS's cyber security mission and we are committed to the security and integrity of the technology on which Americans and others around the world increasingly rely."
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A detailed analysis of the Bloomberg report on technology site The Register noted both Apple and Amazon "would want to keep any highly confidential information and contacts with intelligence services as quiet as possible".
"Even if the story is true, they may be ordered to deny it as vigorously as possible by the Feds on national security grounds. But it is striking quite how vigorous those denials have been on this story," added The Register.
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