Over the last 25 years we've seen a massive change in how we think about information.
In the 1980s, information was mostly still analogue. It was stored on paper, in binders, on shelves and in safes.
Today, of course, almost all information is digital. It's created and stored on computers and transmitted over computer networks.
From a security viewpoint, this means that secret information can now potentially be reached from anywhere in the world; you no longer have to physically be where the information is.
This means that espionage has also gone digital - and while we've seen several cases of nation-state espionage done with backdoors and trojans, we've seen only one documented case of a nation-state doing cyber sabotage with malware. That case is Stuxnet