The greatest strength of a propaganda campaign is also its greatest weakness. An organized and well-funded campaign involves a lot of people communicating with each other, holding meetings, writing documents, making plans and sending e-mails. It's harder and harder to keep a secret these days, particularly among large groups of people. A single leaked e-mail can expose a propaganda effort as a fraud and a lie.
Some experts predict that this problem is impossible to solve and that the Wikileaks scandals mean the age of big, top-down organizations is over – only smaller, self-contained teams will be able to control sensitive information and not get leaked to death.
If you're in a fight against propaganda, getting this sort of evidence from the inside is crucial to undermining the motives and credibility of the other side. It will help level the field. Of course, it may be easier said than done, but it can be explosive if you're successful.