Entries Tagged "Tor"

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Silk Road Author Arrested Due to Bad Operational Security

Details of how the FBI found the administrator of Silk Road, a popular black market e-commerce site.

Despite the elaborate technical underpinnings, however, the complaint portrays Ulbricht as a drug lord who made rookie mistakes. In an October 11, 2011 posting to a Bitcoin Talk forum, for instance, a user called “altoid” advertised he was looking for an “IT pro in the Bitcoin community” to work in a venture-backed startup. The post directed applicants to send responses to “rossulbricht at gmail dot com.” It came about nine months after two previous posts — also made by a user, “altoid,” to shroomery.org and Bitcoin Talk — were among the first to advertise a hidden Tor service that operated as a kind of “anonymous amazon.com.” Both of the earlier posts referenced silkroad420.wordpress.com.

If altoid’s solicitation for a Bitcoin-conversant IT Pro wasn’t enough to make Ulbricht a person of interest in the FBI’s ongoing probe, other digital bread crumbs were sure to arouse agents’ suspicions. The Google+ profile tied to the rossulbricht@gmail.com address included a list of favorite videos originating from mises.org, a website of the “Mises Institute.” The site billed itself as the “world center of the Austrian School of economics” and contained a user profile for one Ross Ulbricht. Several Dread Pirate Roberts postings on Silk Road cited the “Austrian Economic theory” and the works of Mises Institute economists Ludwig von Mises and Murray Rothbard in providing the guiding principles for the illicit drug market.

The clues didn’t stop there. In early March 2012 someone created an account on StackOverflow with the username Ross Ulbricht and the rossulbricht@gmail.com address, the criminal complaint alleged. On March 16 at 8:39 in the morning, the account was used to post a message titled “How can I connect to a Tor hidden service using curl in php?” Less than one minute later, the account was updated to change the user name from Ross Ulbricht to “frosty.” Several weeks later, the account was again updated, this time to replace the Ulbricht gmail address with frosty@frosty.com. In July 2013, a forensic analysis of the hard drives used to run one of the Silk Road servers revealed a PHP script based on curl that contained code that was identical to that included in the Stack Overflow discussion, the complaint alleged.

We already know that it is next to impossible to maintain privacy and anonymity against a well-funded government adversary.

EDITED TO ADD (10/8): Another article.

Posted on October 7, 2013 at 1:35 PMView Comments

How the NSA Attacks Tor/Firefox Users With QUANTUM and FOXACID

The online anonymity network Tor is a high-priority target for the National Security Agency. The work of attacking Tor is done by the NSA‘s application vulnerabilities branch, which is part of the systems intelligence directorate, or SID. The majority of NSA employees work in SID, which is tasked with collecting data from communications systems around the world.

According to a top-secret NSA presentation provided by the whistleblower Edward Snowden, one successful technique the NSA has developed involves exploiting the Tor browser bundle, a collection of programs designed to make it easy for people to install and use the software. The trick identifies Tor users on the Internet and then executes an attack against their Firefox web browser.

The NSA refers to these capabilities as CNE, or computer network exploitation.

The first step of this process is finding Tor users. To accomplish this, the NSA relies on its vast capability to monitor large parts of the Internet. This is done via the agency’s partnership with US telecoms firms under programs codenamed Stormbrew, Fairview, Oakstar and Blarney.

The NSA creates “fingerprints” that detect HTTP requests from the Tor network to particular servers. These fingerprints are loaded into NSA database systems like XKeyscore, a bespoke collection and analysis tool that NSA boasts allows its analysts to see “almost everything” a target does on the Internet.

Using powerful data analysis tools with codenames such as Turbulence, Turmoil and Tumult, the NSA automatically sifts through the enormous amount of Internet traffic that it sees, looking for Tor connections.

Last month, Brazilian TV news show Fantastico showed screenshots of an NSA tool that had the ability to identify Tor users by monitoring Internet traffic.

The very feature that makes Tor a powerful anonymity service, and the fact that all Tor users look alike on the Internet, makes it easy to differentiate Tor users from other web users. On the other hand, the anonymity provided by Tor makes it impossible for the NSA to know who the user is, or whether or not the user is in the US.

After identifying an individual Tor user on the Internet, the NSA uses its network of secret Internet servers to redirect those users to another set of secret Internet servers, with the codename FoxAcid, to infect the user’s computer. FoxAcid is an NSA system designed to act as a matchmaker between potential targets and attacks developed by the NSA, giving the agency opportunity to launch prepared attacks against their systems.

Once the computer is successfully attacked, it secretly calls back to a FoxAcid server, which then performs additional attacks on the target computer to ensure that it remains compromised long-term, and continues to provide eavesdropping information back to the NSA.

Exploiting the Tor browser bundle

Tor is a well-designed and robust anonymity tool, and successfully attacking it is difficult. The NSA attacks we found individually target Tor users by exploiting vulnerabilities in their Firefox browsers, and not the Tor application directly.

This, too, is difficult. Tor users often turn off vulnerable services like scripts and Flash when using Tor, making it difficult to target those services. Even so, the NSA uses a series of native Firefox vulnerabilities to attack users of the Tor browser bundle.

According to the training presentation provided by Snowden, EgotisticalGiraffe exploits a type confusion vulnerability in E4X, which is an XML extension for JavaScript. This vulnerability exists in Firefox 11.0 — 16.0.2, as well as Firefox 10.0 ESR — the Firefox version used until recently in the Tor browser bundle. According to another document, the vulnerability exploited by EgotisticalGiraffe was inadvertently fixed when Mozilla removed the E4X library with the vulnerability, and when Tor added that Firefox version into the Tor browser bundle, but NSA were confident that they would be able to find a replacement Firefox exploit that worked against version 17.0 ESR.

The Quantum system

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-in-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”.

This same technique is used by the Chinese government to block its citizens from reading censored Internet content, and has been hypothesized as a probable NSA attack technique.

The FoxAcid system

According to various top-secret documents provided by Snowden, FoxAcid is the NSA codename for what the NSA calls an “exploit orchestrator,” an Internet-enabled system capable of attacking target computers in a variety of different ways. It is a Windows 2003 computer configured with custom software and a series of Perl scripts. These servers are run by the NSA’s tailored access operations, or TAO, group. TAO is another subgroup of the systems intelligence directorate.

The servers are on the public Internet. They have normal-looking domain names, and can be visited by any browser from anywhere; ownership of those domains cannot be traced back to the NSA.

However, if a browser tries to visit a FoxAcid server with a special URL, called a FoxAcid tag, the server attempts to infect that browser, and then the computer, in an effort to take control of it. The NSA can trick browsers into using that URL using a variety of methods, including the race-condition attack mentioned above and frame injection attacks.

FoxAcid tags are designed to look innocuous, so that anyone who sees them would not be suspicious. http://baseball2.2ndhalfplays.com/nested/attribs/bins/1/define/forms9952_z1zzz.html is an example of one such tag, given in another top-secret training presentation provided by Snowden.

There is no currently registered domain name by that name; it is just an example for internal NSA training purposes.

The training material states that merely trying to visit the homepage of a real FoxAcid server will not result in any attack, and that a specialized URL is required. This URL would be created by TAO for a specific NSA operation, and unique to that operation and target. This allows the FoxAcid server to know exactly who the target is when his computer contacts it.

According to Snowden, FoxAcid is a general CNE system, used for many types of attacks other than the Tor attacks described here. It is designed to be modular, with flexibility that allows TAO to swap and replace exploits if they are discovered, and only run certain exploits against certain types of targets.

The most valuable exploits are saved for the most important targets. Low-value exploits are run against technically sophisticated targets where the chance of detection is high. TAO maintains a library of exploits, each based on a different vulnerability in a system. Different exploits are authorized against different targets, depending on the value of the target, the target’s technical sophistication, the value of the exploit, and other considerations.

In the case of Tor users, FoxAcid might use EgotisticalGiraffe against their Firefox browsers.

According to a top-secret operational management procedures manual provided by Snowden, once a target is successfully exploited it is infected with one of several payloads. Two basic payloads mentioned in the manual are designed to collect configuration and location information from the target computer so an analyst can determine how to further infect the computer.

These decisions are made in part by the technical sophistication of the target and the security software installed on the target computer, called Personal Security Products or PSP, in the manual.

FoxAcid payloads are updated regularly by TAO. For example, the manual refers to version 8.2.1.1 of one of them.

FoxAcid servers also have sophisticated capabilities to avoid detection and to ensure successful infection of its targets. The operations manual states that a FoxAcid payload with the codename DireScallop can circumvent commercial products that prevent malicious software from making changes to a system that survive a reboot process.

The NSA also uses phishing attacks to induce users to click on FoxAcid tags.

TAO additionally uses FoxAcid to exploit callbacks — which is the general term for a computer infected by some automatic means — calling back to the NSA for more instructions and possibly to upload data from the target computer.

According to a top-secret operational management procedures manual, FoxAcid servers configured to receive callbacks are codenamed FrugalShot. After a callback, the FoxAcid server may run more exploits to ensure that the target computer remains compromised long term, as well as install “implants” designed to exfiltrate data.

By 2008, the NSA was getting so much FoxAcid callback data that they needed to build a special system to manage it all.

This essay previously appeared in the Guardian. It is the technical article associated with this more general-interest article. I also wrote two commentaries on the material.

EDITED TO ADD: Here is the source material we published. The Washington Post published its own story independently, based on some of the same source material and some new source material.

Here’s the official US government response to the story.

The Guardian decided to change the capitalization of the NSA codenames. They should properly be in all caps: FOXACID, QUANTUMCOOKIE, EGOTISTICALGIRAFFE, TURMOIL, and so on.

This is the relevant quote from the Spiegel article:

According to the slides in the GCHQ presentation, the attack was directed at several Belgacom employees and involved the planting of a highly developed attack technology referred to as a “Quantum Insert” (“QI”). It appears to be a method with which the person being targeted, without their knowledge, is redirected to websites that then plant malware on their computers that can then manipulate them. Some of the employees whose computers were infiltrated had “good access” to important parts of Belgacom’s infrastructure, and this seemed to please the British spies, according to the slides.

That should be “QUANTUMINSERT.” This is getting frustrating. The NSA really should release a style guide for press organizations publishing their secrets.

And the URL in the essay (now redacted at the Guardian site) was registered within minutes of the story posting, and is being used to serve malware. Don’t click on it.

Posted on October 7, 2013 at 6:24 AMView Comments

New NSA Leak Shows MITM Attacks Against Major Internet Services

The Brazilian television show “Fantastico” exposed an NSA training presentation that discusses how the agency runs man-in-the-middle attacks on the Internet. The point of the story was that the NSA engages in economic espionage against Petrobras, the Brazilian giant oil company, but I’m more interested in the tactical details.

The video on the webpage is long, and includes what I assume is a dramatization of an NSA classroom, but a few screen shots are important. The pages from the training presentation describe how the NSA’s MITM attack works:

However, in some cases GCHQ and the NSA appear to have taken a more aggressive and controversial route — on at least one occasion bypassing the need to approach Google directly by performing a man-in-the-middle attack to impersonate Google security certificates. One document published by Fantastico, apparently taken from an NSA presentation that also contains some GCHQ slides, describes “how the attack was done” to apparently snoop on SSL traffic. The document illustrates with a diagram how one of the agencies appears to have hacked into a target’s Internet router and covertly redirected targeted Google traffic using a fake security certificate so it could intercept the information in unencrypted format.

Documents from GCHQ’s “network exploitation” unit show that it operates a program called “FLYING PIG” that was started up in response to an increasing use of SSL encryption by email providers like Yahoo, Google, and Hotmail. The FLYING PIG system appears to allow it to identify information related to use of the anonymity browser Tor (it has the option to query “Tor events“) and also allows spies to collect information about specific SSL encryption certificates.

It’s that first link — also here — that shows the MITM attack against Google and its users.

Another screenshot implies is that the 2011 DigiNotar hack was either the work of the NSA, or exploited by the NSA.

Here’s another story on this.

Posted on September 13, 2013 at 6:23 AMView Comments

Disguising Tor Traffic as Skype Video Calls

One of the problems with Tor traffic is that it can de detected and blocked. Here’s SkypeMorph, a clever system that disguises Tor traffic as Skype video traffic.

To prevent the Tor traffic from being recognized by anyone analyzing the network flow, SkypeMorph uses what’s known as traffic shaping to convert Tor packets into User Datagram Protocol packets, as used by Skype. The traffic shaping also mimics the sizes and timings of packets produced by normal Skype video conversations. As a result, outsiders observing the traffic between the end user and the bridge see data that looks identical to a Skype video conversation.

The SkypeMorph developers chose Skype because the software is widely used throughout the world, making it hard for governments to block it without arousing widespread criticism. The developers picked the VoIP client’s video functions because its flow of packets more closely resembles Tor traffic. Voice communications, by contrast, show long pauses in transmissions, as one party speaks and the other listens.

Posted on April 13, 2012 at 7:08 AMView Comments

Tor Arms Race

Iran blocks Tor, and Tor releases a workaround on the same day.

How did the filter work technically? Tor tries to make its traffic look like a web browser talking to an https web server, but if you look carefully enough you can tell some differences. In this case, the characteristic of Tor’s SSL handshake they looked at was the expiry time for our SSL session certificates: we rotate the session certificates every two hours, whereas normal SSL certificates you get from a certificate authority typically last a year or more. The fix was to simply write a larger expiration time on the certificates, so our certs have more plausible expiry times.

Posted on September 26, 2011 at 6:41 AMView Comments

Identifying Tor Users Through Insecure Applications

Interesting research: “One Bad Apple Spoils the Bunch: Exploiting P2P Applications to Trace and Profile Tor Users“:

Abstract: Tor is a popular low-latency anonymity network. However, Tor does not protect against the exploitation of an insecure application to reveal the IP address of, or trace, a TCP stream. In addition, because of the linkability of Tor streams sent together over a single circuit, tracing one stream sent over a circuit traces them all. Surprisingly, it is unknown whether this linkability allows in practice to trace a significant number of streams originating from secure (i.e., proxied) applications. In this paper, we show that linkability allows us to trace 193% of additional streams, including 27% of HTTP streams possibly originating from “secure” browsers. In particular, we traced 9% of Tor streams carried by our instrumented exit nodes. Using BitTorrent as the insecure application, we design two attacks tracing BitTorrent users on Tor. We run these attacks in the wild for 23 days and reveal 10,000 IP addresses of Tor users. Using these IP addresses, we then profile not only the BitTorrent downloads but also the websites visited per country of origin of Tor users. We show that BitTorrent users on Tor are over-represented in some countries as compared to BitTorrent users outside of Tor. By analyzing the type of content downloaded, we then explain the observed behaviors by the higher concentration of pornographic content downloaded at the scale of a country. Finally, we present results suggesting the existence of an underground BitTorrent ecosystem on Tor.

Posted on March 25, 2011 at 6:38 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.