And why would they? Post-911 warrantless wiretapping practices are well known, NSA-style data collection was well-rumored, and we all knew the Department of Homeland Security was already scanning emails for red-flag keywords. Of course terrorists would take precautions. Bloomberg elaborates:
In a January 2012 report titled “Jihadism on the Web: A Breeding Ground for Jihad in the Modern Age,” the Dutch General Intelligence and Security Service drew a convincing picture of an Islamist Web underground centered around “core forums.” These websites are part of the Deep Web, or Undernet, the multitude of online resources not indexed by commonly used search engines.
In 2010, Google estimated that it had indexed just 0.004% of the internet—meaning the vast majority of the web is open for surreptitious message-sending business. Terrorists simply aren’t dumb enough to discuss their secret plans over Skype or to email each other confidential information on Gmail.
So, essentially, the NSA is deeply compromising our privacy so that it can do an extremely shitty job of looking for terrorists. Nice.