Schneier on Security

In the wake of Wikileaks, the Department of Defense has stepped up its game to stop leaked documents from making their way into the hands of undesirables—be they enemy forces or concerned citizens. A new piece of software has created a way to do this by generating realistic, fake documents that phone home when they’re accessed, serving the dual purpose of providing false intelligence and helping identify the culprit.

Details aside, this kind of thing falls into the general category of data tracking. It doesn’t even have to be fake documents; you could imagine some sort of macro embedded into Word or pdf documents that phones home when the document is opened. (I have no idea if you actually can do it with those formats, but the concept is plausible.) This allows the owner of a document to track when, and possibly by what computer, a document is opened.

But by far the biggest drawback from this tech is the possibility of false positives. If you seed a folder full of documents with a large number of fakes, how often do you think an authorized user will accidentally double click on the wrong file? And what if they act on the false information? Sure, this will prevent hackers from blindly trusting that every document on a server is correct, but we bet it won’t take much to look into the code of a document and spot the fake, either.

I’m less worried about false positives, and more concerned by how easy it is to get around this sort of thing. Detach your computer from the Internet, and the document no longer phones home. A fix is to combine the system with an encryption scheme that requires a remote key. Now the document has to phone home before it can be viewed. Of course, once someone is authorized to view the document, it would be easy to create an unprotected copy—screen captures, if nothing else—to forward along,

While potentially interesting, this sort of technology is not going to prevent large data leaks. But it’s good to see research.