People who know what they're doing — like renegade National Security Agency analyst Edward Snowden and professional terrorists at Al Qaeda — find it relatively easy to avoid detection.

From the Associated Press:

Jihadist technology may now be so sophisticated and secretive, experts say, that many communications avoid detection by National Security Agency programs that were specifically designed to uncover terror plots.

And why is that?

From AP:

[Because] Al-Qaida leaders ... [use] ... a multi-layered subterfuge to pass messages from couriers to tech-savvy underlings to attackers.

... over the past decade [jihadists] have developed systems that blend encryption programs with anonymity software to hide their tracks ...

This is not unlike what Snowden did when he first communicated with documentary filmmaker Laura Poitras.

From the New York Times:

[Poitras] sent [Snowden] her public key — allowing him or her to send an encrypted e-mail that only Poitras could open, with her private key ...

[Snowden sent] instructions for creating an even more secure system to protect their exchanges. Promising sensitive information, the stranger told Poitras to select long pass phrases that could withstand a brute-force attack by networked computers. “Assume that your adversary is capable of a trillion guesses per second,” the stranger wrote.

What Snowden and Poitras likely did was use a highly encrypted email service (like Lavabit) to exchange "the key."

That was their most vulnerable time. Since Lavabit just closed up shop presumably under Federal pressure, we can safely assume that key wasn't snooped.

Then Snowden and Poitras set up another line of communication (possibly using another service) using that highly complex (40 characters) key or password to communicate.

Essentially uncrackable.

Now it's not even in the slightest bit of irony that we hear how potential terrorists use multi-layered encryption processes much as Snowden did — with the addition of one element, on-foot couriers carrying thumb drives to tech centers.

The AP reports that "so frustrated was the CIA at one point, the spy agency considered killing the couriers passing messages in an attempt to disrupt the terrorist group’s plans, said a former senior U.S. official."

One thing still works though: old-school human intel.

From AP:

.... planting a spy in the online forum. That has happened in the past, according to intelligence experts, most recently in a case now in federal court in Miami in which prosecutors say an undercover FBI agent snared two alleged terrorist recruiters in an online chat room by posing as a financial middleman.

Although that method takes considerably more time than just clicking okay on a computer and scooping up communications — arguably the NSA's dream capability.

Needless to say, the Feds maintain that they caught wind of something, which is what led to the Embassy closings in Yemen (and elsewhere):

Intelligence officials have suggested that the plot was detected, in part at least, through NSA surveillance programs that have been under harsh worldwide criticism for privacy intrusions in the name of national security.