New material leaked by Edward Snowden shows which Internet security protocols the NSA had beaten as of 2012 and which encryption tools were still stymying cyber spies.

Digital spies in the National Security Administration cracked Skype's encryption back in 2011 and can make quick work of the VPNs many businesses believe make their communications secure.

But more robust security protocols and encryption techniques may still be secure from prying NSA eyes, according to documents revealed by former NSA contractor Edward Snowden.

Der Spiegel has the rundown on the NSA's battle against what its training documents described as the "threat" of secure Internet communication. Snowden's documentation is several years old now, of course. Whether or not U.S. cyber spies have managed to crack some of the toughest nuts in the intervening years, like Tor network communications, isn't known.

First, the security layers that the NSA considered to be "trivial," "minor," or "moderate" challenges to get through as of 2012. These include such tasks as simply monitoring a document as it travels across the Internet, spying on Facebook chats, and decrypting mail.ru emails, according to the Snowden documents.

But there are others that NSA cryptologists have had a much tougher time defeating, Der Spiegel noted, as documented in their sorting of threats "into five levels corresponding to the degree of the difficulty of the attack and the outcome, ranging from 'trivial' to a 'catastrophic.'"

"Things first become troublesome at the fourth level," according to Der Spiegel, which culled its report from a specific NSA presentation on Internet security.

As of 2012, the agency was having "major problems in its attempts to decrypt messages sent through heavily encrypted email service providers like Zoho or in monitoring users of the Tor network," the newspaper reported. Other "major," or fourth-level challenges included open-source protocols like Truecrypt and OTR instant-messaging encryption.

"Experts agree it is far more difficult for intelligence agencies to manipulate open source software programs than many of the closed systems developed by companies like Apple and Microsoft. Since anyone can view free and open source software, it becomes difficult to insert secret back doors without it being noticed," Der Spiegel noted.

The toughest method of Internet communication for the NSA to crack? It's not any one dark Internet tool but rather a bunch of them layered on top of each other, according to the Snowden documents.

Original post:

NSA Docs Reveal Spy-Proof Encryption Tools