In May, the U.S. government circulated a wanted poster showing five members of a shadowy Chinese cyber-espionage unit. No one expects any of them to turn up in a U.S. courtroom, but the object of the publicity was twofold. First, it was intended to show the Chinese that the U.S. government takes their operations seriously, that it can and will retaliate in some unspecified way. It is as pointless to ask the Chinese (and many others) to abandon cyber espionage as it would be to seek an international treaty barring any other kind of spying. The spies would stay in business, but some naive governments would abandon counterespionage, and cease any spying of their own.
World Naval Developments - Beware the Cyber Spies
By Norman Friedman