By now, most people will have read about the Canadian pedophile from Maple Ridge who is being sought in Thailand. The story is a shocking and lamentable one, but I want to concentrate here on the technical aspect. INTERPOL released images of the man, claiming they had undone the Photoshop ‘twirl’ effect that had been used to disguise him initially in compromising photos. While this claim has been widely reported in the media, there is at least some reason to question it. It is also possible that INTERPOL is concealing the fact that it received unaltered photos from another source, which could have been anything from intercepted emails to files recovered from an improperly erased camera memory card. It could even have been recovered from the EXIF metadata thumbnails many cameras produce. It is also possible this particular effect is so easy to reverse (and that the technique is so widely known to exist) that INTERPOL saw no value in keeping their methods secret. A quick Google search suggests that the ‘twist’ effect is a plausible candidate for easy reversal.
Providing an alternative story to explain the source of information is an ancient intelligence tactic. For instance, during the Second World War an imaginary spy ring was created by the British and used to justify how they had some of the information that had actually been obtained through cracked ENIGMA transmissions at Bletchley Park. Some have argued that the Coventry Bombing was known about in advance by British intelligence due to deciphered messages, but they decided not to evacuate the city because they did not want to reveal to the enemy that their ciphers had been compromised. While this particular example may or may not be historically accurate, it illustrates the dilemma of somebody in possession of important intelligence acquired in a sensitive manner.
Cover stories can conceal sources and methods in other ways. A few years ago, it was claimed that Pervez Musharraf had escaped having his motorcade bombed, due to a radio jammer. While that is certainly possible, it seems unlikely that his guards would have reported the existence of the system if it had played such a crucial role. More likely, they got tipped off from an informant in the group responsible, an agent they had implanted in it, or some sort of communication intercept. Given how it is now widely known that email messages and phone calls worldwide are regularly intercepted by governments, I imagine a lot of spies and informants are being protected by false stories about communication intercepts.
In short, it is fair to say that any organization concerned with intelligence gathering will work diligently to protect their sources and methods. After all, these are what ensure their future access to privileged information in the future. While there is a slim chance INTERPOL intentionally revealed their ability to unscramble photographs as some sort of deterrent, it seems unlikely. This situation will simply encourage people to use more aggressive techniques to conceal their faces in the future. It is also possible that, in this case, they felt that getting the man’s image out was more important than protecting their methods. In my opinion, it seems most likely that ‘twist’ really is easy to unscramble and that they saw little value in not publicizing this fact. That said, it remains possible that a more complex collection of tactics and calculations has been applied.