> we can conclude it's not the US government because Yahoo is willing and legally able to publicly disclose it.
This implies a potentially fatal assumption that IC agencies perform clandestine activities with prior notice to mission targets.
This implies a potentially fatal assumption that IC agencies perform clandestine activities with prior notice to mission targets.
It's possible however that agency doesn't realise it's a clandestine operation by another US agency. Or they do, but now the operation is complete (this was three years ago) and they want a way of informing yahoo about the breach without admitting who was behind it in the first place.