These days, it's rare that we learn something new from the Snowden documents. But Ben Buchanan found something interesting. The NSA penetrates enemy networks in order to enhance our defensive capabilities.
The data the NSA collected by penetrating BYZANTINE CANDOR's networks had concrete forward-looking defensive value. It included information on the adversary's "future targets," including "bios of senior White House officials, [cleared defense contractor] employees, [United States government] employees" and more. It also included access to the "source code and [the] new tools" the Chinese used to conduct operations. The computers penetrated by the NSA also revealed information about the exploits in use. In effect, the intelligence gained from the operation, once given to network defenders and fed into automated systems, was enough to guide and enhance the United States' defensive efforts.
This case alludes to important themes in network defense. It shows the persistence of talented adversaries, the creativity of clever defenders, the challenge of getting actionable intelligence on the threat, and the need for network architecture and defenders capable of acting on that information. But it also highlights an important point that is too often overlooked: not every intrusion is in service of offensive aims. There are genuinely defensive reasons for a nation to launch intrusions against another nation's networks.
Other Snowden files show what the NSA can do when it gathers this data, describing an interrelated and complex set of United States programs to collect intelligence and use it to better protect its networks. The NSA's internal documents call this "foreign intelligence in support of dynamic defense." The gathered information can "tip" malicious code the NSA has placed on servers and computers around the world. Based on this tip, one of the NSA's nodes can act on the information, "inject[ing a] response onto the Internet towards [the] target." There are a variety of responses that the NSA can inject, including resetting connections, delivering malicious code, and redirecting internet traffic.
Similarly, if the NSA can learn about the adversary's "tools and tradecraft" early enough, it can develop and deploy "tailored countermeasures" to blunt the intended effect. The NSA can then try to discern the intent of the adversary and use its countermeasure to mitigate the attempted intrusion. The signals intelligence agency feeds information about the incoming threat to an automated system deployed on networks that the NSA protects. This system has a number of capabilities, including blocking the incoming traffic outright, sending unexpected responses back to the adversary, slowing the traffic down, and "permitting the activity to appear [to the adversary] to complete without disclosing that it did not reach [or] affect the intended target."
These defensive capabilities appear to be actively in use by the United States against a wide range of threats. NSA documents indicate that the agency uses the system to block twenty-eight major categories of threats as of 2011. This includes action against significant adversaries, such as China, as well as against non-state actors. Documents provide a number of success stories. These include the thwarting of a BYZANTINE HADES intrusion attempt that targeted four high-ranking American military leaders, including the Chief of Naval Operations and the Chairman of the Joint Chiefs of Staff; the NSA's network defenders saw the attempt coming and successfully prevented any negative effects. The files also include examples of successful defense against Anonymous and against several other code-named entities.
I recommend Buchanan's book: The Cybersecurity Dilemma: Hacking, Trust and Fear Between Nations.