The Worst Spy Networks in the First World War?

In World War I there were operations behind enemy lines run by the founder of what today we call MI6. We had spies embedded all across European capitals, but particularly in the main headquarters in Vienna. It's like a web, and the early form of MI6 would have its key heads of station in European capitals and elsewhere in the world. Those figures would actually run their own agents, their own spies, and send intelligence back to London. So this is going on, it's a long game, about thousands of years to biblical times, there's always been espionage.