Repeat a lie three times and someone is bound to use it and reference you as a source of truth. Especially if the author of the unsubstantiated claim is from any intelligence agency. For some reason they are beyond fact-checking by news agencies.
Cyber attacks can be expensive: one unidentified London-listed company incurred losses of 800 million pounds ($1.29 billion) in a cyber attack several years ago, according to the British security services.
I do not remember any story about a company losing that amount of money to “unforeseen losses” and I am sure the markets would have reacted according to the size of the loss. It would’ve made the news, no doubt about it. No such thing is recorded. Which leads to the simplest of conclusions: either the whole story is made up, or the magnitude of the loss was made up.