TS, SI, FVEY: what the Pentagon leak initials tell us about modern spying

Everything from the gamer leaker to the global spread of potential sources reveals much about the anxiety-making conditions of 21st-century espionage

After TS (top secret), two other letters repeatedly stand out throughout the leaked Pentagon files: SI. The letters stand for special intelligence, and signify that the information has been derived from signals intelligence work. This encompasses eavesdropping, surveillance and even backdoor access to information systems - all part of a panopticon of global, US-led intelligence collection.

Signals intelligence told the 1.25 million Americans with top secret clearance - and sometimes their British allies - that Russia had made marginal battlefield gains in Ukraine, that the Wagner group may be allowed to restart recruiting prisoners, and even that Russian hackers had gained control of a Canadian gas pipeline they hope to explode.