Reuters reported that the letter, sent by its vice-president for information security on Sunday, said Apple had repeatedly searched for evidence to substantiate the claims made by Bloomberg reporters Jordan Robertson and Michael Riley but had been unable to find anything.
The letter also pointed out that though there were 17 anonymous sources cited in the story, some of the claims rested on a few sources, and some on a single source.
In its story, Bloomberg claimed security testing by Amazon in 2015 had revealed the existence of tiny chips that were not part of the original mainboard design and that this led to an extensive investigation by US Government agencies which found servers built using these boards in data centres belonging to the Department of Defence, on warships, and for processing data being handled by CIA drones.
A few years ago, Robertson and Riley put out a story, claiming that the US Government ad prior knowledge of the Heartbleed bug, a serious vulnerability in OpenSSL, before it was announced. Bloomberg did not issue a follow-up after the story was denied.
In the letter, Stathakopoulos wrote: "Apple’s proprietary security tools are continuously scanning for precisely this kind of outbound traffic, as it indicates the existence of malware or other malicious activity. Nothing was ever found."
He also repeated the claims made by Apple soon after the Bloomberg story was published, that it had never found any evidence of hardware implants in servers it had used, or that it had ever contacted the FBI about such matters.
Stathakopoulos offered to brief US politicians about the report in the coming week.
Apple and Amazon have already issued detailed denials about the claims made by Robertson and Riley. The UK National Cyber Security Centre and the US Department of Homeland Security have backed the companies in their denials.
And a former Apple general counsel, Bruce Sewell, said on Saturday that he had contacted the FBI about the Bloomberg claims and been told that the agency knew nothing about them.
Link to Apple's letter courtesy Forbes