We already covered the latest Guardian report on the NSA and GCHQ's attempts to compromise Tor
. While those have failed to directly break Tor, they were more successful effectively exploiting vulnerabilities in Firefox to target certain Tor users. Bruce Schneier has a more focused article on how those attacks worked
, and as a part of that, detailed how the NSA and GCHQ are effectively able to do man-in-the-middle attacks on giant websites, something that is really only possible because of the major telcos letting the NSA put servers directly off the backbone. As we noted last month, buried in one of the earlier Snowden leaks was the news that the GCHQ and NSA were likely running man-in-the-middle attacks on Google
. The latest leaks show why those work. As Schneier explains:
To trick targets into visiting a FoxAcid server, the NSA relies on its secret partnerships with US telecoms companies. As part of the Turmoil system, the NSA places secret servers, codenamed Quantum, at key places on the internet backbone. This placement ensures that they can react faster than other websites can. By exploiting that speed difference, these servers can impersonate a visited website to the target before the legitimate website can respond, thereby tricking the target's browser to visit a Foxacid server.
In the academic literature, these are called "man-on-the-middle" attacks, and have been known to the commercial and academic security communities. More specifically, they are examples of "man-on-the-side" attacks.
They are hard for any organization other than the NSA to reliably execute, because they require the attacker to have a privileged position on the internet backbone, and exploit a "race condition" between the NSA server and the legitimate website. This top-secret NSA diagram, made public last month, shows a Quantum server impersonating Google in this type of attack.
The NSA uses these fast Quantum servers to execute a packet injection attack, which surreptitiously redirects the target to the FoxAcid server. An article in the German magazine Spiegel, based on additional top secret Snowden documents, mentions an NSA developed attack technology with the name of QuantumInsert that performs redirection attacks. Another top-secret Tor presentation provided by Snowden mentions QuantumCookie to force cookies onto target browsers, and another Quantum program to "degrade/deny/disrupt Tor access".
Schneier also notes that this is basically the same technique the Chinese have used for their Great Firewall. In other words, the complicit nature of the telcos in basically giving the NSA and GCHQ incredibly privileged access to the backbone is part of what allows them to conduct those kinds of man-in-the-middle attacks. It still amazes me that there isn't more outrage over the role of the major telcos in all of this.
The other interesting thing about the FoxAcid servers is that it's basically a system that gives the NSA a rotating menu of ways to exploit a visitor who gets hooked on one of their servers. It also notes that the NSA is pretty careful about how it uses various exploits, such that "low-value exploits" are used against more technically sophisticated targets, recognizing that they're more likely to be discovered, and thus burned. They save the "most valuable exploits" for less technically savvy targets, and also the most important targets. This is hardly surprising, but interesting to see the level with which they plan these things out.