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Fingerprinting Burner Phones

In one of the documents recently released by the NSA as a result of an EFF lawsuit, there’s discussion of a specific capability of a call records database to identify disposable “burner” phones.

Let’s consider, then, the very specific data this query tool was designed to return: The times and dates of the first and last call events, but apparently not the times and dates of calls between those endpoints. In other words, this tool is supporting analytic software that only cares when a phone went online, and when it stopped being used. It also gets the total number of calls, and the ratio of unique contacts to calls, but not the specific numbers contacted. Why, exactly, would this limited set of information be useful? And why, in particular, might you want to compare that information across a large number of phones there’s not yet any particular reason to suspect?

One possibility that jumps out at me—and perhaps anyone else who’s a fan of The Wire—is that this is the kind of information you would want if you were trying to identify disposable prepaid “burner” phones being used by a target who routinely cycles through cell phones as a countersurveillance tactic. The number of unique contacts and call/contact ratio would act as a kind of rough fingerprint—you’d assume a phone being used for dedicated clandestine purposes to be fairly consistent on that score—while the first/last call dates help build a timeline: You’re looking for a series of phones that are used for a standard amount of time, and then go dead just as the next phone goes online.

Consider this another illustration of the value of metadata.

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Posted on October 14, 2013 at 6:37 AM • View Comments

New Low in Election Fraud

Azerbaijan achieves a new low in electoral fraud: the government accidentally publishes the results of the election before the polls open.

The mistake came when an electoral commission accidentally published results showing a victory for Ilham Aliyev, the country’s long-standing President, a day before voting. Meydan TV, an online channel critical of the government, released a screenshot from a mobile app for the Azerbaijan Central Election Commission which showed that Mr Aliyev had received 72.76 per cent of the vote compared with 7.4 per cent for the opposition candidate, Jamil Hasanli. The screenshot also indicates that the app displayed information about how many people voted at various times during the day. Polls opened at 8am.

Here’s another article.

But luckily, former US legislators are monitoring everything:

But observers from other delegations, including a group of former members of the United States House of Representatives, said the voting on Wednesday was clean and efficient. Mr. Aliyev, thanking voters in a televised statement, called the elections “free and transparent.”

Former Representative Michael E. McMahon, a Democrat from Staten Island, called the vote “honest, fair and really efficient.”

“There were much shorter lines than in America, and no hanging chads“—a reference to the disputed ballots in the United States presidential race in 2000.

Long lines? Hanging chads? These people have no idea how the big boys steal elections.

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Posted on October 11, 2013 at 12:33 PM • View Comments

Air Gaps

Since I started working with Snowden’s documents, I have been using a number of tools to try to stay secure from the NSA. The advice I shared included using Tor, preferring certain cryptography over others, and using public-domain encryption wherever possible.

I also recommended using an air gap, which physically isolates a computer or local network of computers from the Internet. (The name comes from the literal gap of air between the computer and the Internet; the word predates wireless networks.)

But this is more complicated than it sounds, and requires explanation.

Since we know that computers connected to the Internet are vulnerable to outside hacking, an air gap should protect against those attacks. There are a lot of systems that use—or should use—air gaps: classified military networks, nuclear power plant controls, medical equipment, avionics, and so on.

Osama Bin Laden used one. I hope human rights organizations in repressive countries are doing the same.

Air gaps might be conceptually simple, but they’re hard to maintain in practice. The truth is that nobody wants a computer that never receives files from the Internet and never sends files out into the Internet. What they want is a computer that’s not directly connected to the Internet, albeit with some secure way of moving files on and off.

But every time a file moves back or forth, there’s the potential for attack.

And air gaps have been breached. Stuxnet was a US and Israeli military-grade piece of malware that attacked the Natanz nuclear plant in Iran. It successfully jumped the air gap and penetrated the Natanz network. Another piece of malware named agent.btz, probably Chinese in origin, successfully jumped the air gap protecting US military networks.

These attacks work by exploiting security vulnerabilities in the removable media used to transfer files on and off the air-gapped computers.

Since working with Snowden’s NSA files, I have tried to maintain a single air-gapped computer. It turned out to be harder than I expected, and I have ten rules for anyone trying to do the same:

  1. When you set up your computer, connect it to the Internet as little as possible. It’s impossible to completely avoid connecting the computer to the Internet, but try to configure it all at once and as anonymously as possible. I purchased my computer off-the-shelf in a big box store, then went to a friend’s network and downloaded everything I needed in a single session. (The ultra-paranoid way to do this is to buy two identical computers, configure one using the above method, upload the results to a cloud-based anti-virus checker, and transfer the results of that to the air gap machine using a one-way process.)

  2. Install the minimum software set you need to do your job, and disable all operating system services that you won’t need. The less software you install, the less an attacker has available to exploit. I downloaded and installed OpenOffice, a PDF reader, a text editor, TrueCrypt, and BleachBit. That’s all. (No, I don’t have any inside knowledge about TrueCrypt, and there’s a lot about it that makes me suspicious. But for Windows full-disk encryption it’s that, Microsoft’s BitLocker, or Symantec’s PGPDisk—and I am more worried about large US corporations being pressured by the NSA than I am about TrueCrypt.)

  3. Once you have your computer configured, never directly connect it to the Internet again. Consider physically disabling the wireless capability, so it doesn’t get turned on by accident.

  4. If you need to install new software, download it anonymously from a random network, put it on some removable media, and then manually transfer it to the air-gapped computer. This is by no means perfect, but it’s an attempt to make it harder for the attacker to target your computer.

  5. Turn off all autorun features. This should be standard practice for all the computers you own, but it’s especially important for an air-gapped computer. Agent.btz used autorun to infect US military computers.

  6. Minimize the amount of executable code you move onto the air-gapped computer. Text files are best. Microsoft Office files and PDFs are more dangerous, since they might have embedded macros. Turn off all macro capabilities you can on the air-gapped computer. Don’t worry too much about patching your system; in general, the risk of the executable code is worse than the risk of not having your patches up to date. You’re not on the Internet, after all.

  7. Only use trusted media to move files on and off air-gapped computers. A USB stick you purchase from a store is safer than one given to you by someone you don’t know—or one you find in a parking lot.

  8. For file transfer, a writable optical disk (CD or DVD) is safer than a USB stick. Malware can silently write data to a USB stick, but it can’t spin the CD-R up to 1000 rpm without your noticing. This means that the malware can only write to the disk when you write to the disk. You can also verify how much data has been written to the CD by physically checking the back of it. If you’ve only written one file, but it looks like three-quarters of the CD was burned, you have a problem. Note: the first company to market a USB stick with a light that indicates a write operation—not read or write; I’ve got one of those—wins a prize.

  9. When moving files on and off your air-gapped computer, use the absolute smallest storage device you can. And fill up the entire device with random files. If an air-gapped computer is compromised, the malware is going to try to sneak data off it using that media. While malware can easily hide stolen files from you, it can’t break the laws of physics. So if you use a tiny transfer device, it can only steal a very small amount of data at a time. If you use a large device, it can take that much more. Business-card-sized mini-CDs can have capacity as low as 30 MB. I still see 1-GB USB sticks for sale.

  10. Consider encrypting everything you move on and off the air-gapped computer. Sometimes you’ll be moving public files and it won’t matter, but sometimes you won’t be, and it will. And if you’re using optical media, those disks will be impossible to erase. Strong encryption solves these problems. And don’t forget to encrypt the computer as well; whole-disk encryption is the best.

One thing I didn’t do, although it’s worth considering, is use a stateless operating system like Tails. You can configure Tails with a persistent volume to save your data, but no operating system changes are ever saved. Booting Tails from a read-only DVD—you can keep your data on an encrypted USB stick—is even more secure. Of course, this is not foolproof, but it greatly reduces the potential avenues for attack.

Yes, all this is advice for the paranoid. And it’s probably impossible to enforce for any network more complicated than a single computer with a single user. But if you’re thinking about setting up an air-gapped computer, you already believe that some very powerful attackers are after you personally. If you’re going to use an air gap, use it properly.

Of course you can take things further. I have met people who have physically removed the camera, microphone, and wireless capability altogether. But that’s too much paranoia for me right now.

This essay previously appeared on Wired.com.

EDITED TO ADD: Yes, I am ignoring TEMPEST attacks. I am also ignoring black bag attacks against my home.

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Posted on October 11, 2013 at 6:45 AM • View Comments

A New Postal Privacy Product

The idea is basically to use indirection to hide physical addresses. You would get a random number to give to your correspondents, and the post office would use that number to determine your real address. No security against government surveillance, but potentially valuable nonetheless.

Here are a bunch of documents.

I honestly have no idea what’s going on. It seems to be something the US government is considering, but it was not proposed by the US Postal Service. This guy is proposing the service.

EDITED TO ADD (10/11): Sai has contacted me and asked that people refrain from linking to or writing about this for now, until he posts some more/better information. I’ll update this post with a new link when he sends it to me.

EDITED TO ADD (10/17): Sai has again contacted me, saying that he has posted the more/better information, and that the one true link for the proposal is here.

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Posted on October 9, 2013 at 1:08 PM • View Comments

The NSA's New Risk Analysis

As I recently reported in the Guardian, the NSA has secret servers on the Internet that hack into other computers, codename FOXACID. These servers provide an excellent demonstration of how the NSA approaches risk management, and exposes flaws in how the agency thinks about the secrecy of its own programs.

Here are the FOXACID basics: By the time the NSA tricks a target into visiting one of those servers, it already knows exactly who that target is, who wants him eavesdropped on, and the expected value of the data it hopes to receive. Based on that information, the server can automatically decide what exploit to serve the target, taking into account the risks associated with attacking the target, as well as the benefits of a successful attack. According to a top-secret operational procedures manual provided by Edward Snowden, an exploit named Validator might be the default, but the NSA has a variety of options. The documentation mentions United Rake, Peddle Cheap, Packet Wrench, and Beach Head—all delivered from a FOXACID subsystem called Ferret Cannon. Oh how I love some of these code names. (On the other hand, EGOTISTICALGIRAFFE has to be the dumbest code name ever.)

Snowden explained this to Guardian reporter Glenn Greenwald in Hong Kong. If the target is a high-value one, FOXACID might run a rare zero-day exploit that it developed or purchased. If the target is technically sophisticated, FOXACID might decide that there’s too much chance for discovery, and keeping the zero-day exploit a secret is more important. If the target is a low-value one, FOXACID might run an exploit that’s less valuable. If the target is low-value and technically sophisticated, FOXACID might even run an already-known vulnerability.

We know that the NSA receives advance warning from Microsoft of vulnerabilities that will soon be patched; there’s not much of a loss if an exploit based on that vulnerability is discovered. FOXACID has tiers of exploits it can run, and uses a complicated trade-off system to determine which one to run against any particular target.

This cost-benefit analysis doesn’t end at successful exploitation. According to Snowden, the TAO—that’s Tailored Access Operations—operators running the FOXACID system have a detailed flowchart, with tons of rules about when to stop. If something doesn’t work, stop. If they detect a PSP, a personal security product, stop. If anything goes weird, stop. This is how the NSA avoids detection, and also how it takes mid-level computer operators and turn them into what they call “cyberwarriors.” It’s not that they’re skilled hackers, it’s that the procedures do the work for them.

And they’re super cautious about what they do.

While the NSA excels at performing this cost-benefit analysis at the tactical level, it’s far less competent at doing the same thing at the policy level. The organization seems to be good enough at assessing the risk of discovery—for example, if the target of an intelligence-gathering effort discovers that effort—but to have completely ignored the risks of those efforts becoming front-page news.

It’s not just in the U.S., where newspapers are heavy with reports of the NSA spying on every Verizon customer, spying on domestic e-mail users, and secretly working to cripple commercial cryptography systems, but also around the world, most notably in Brazil, Belgium, and the European Union. All of these operations have caused significant blowback—for the NSA, for the U.S., and for the Internet as a whole.

The NSA spent decades operating in almost complete secrecy, but those days are over. As the corporate world learned years ago, secrets are hard to keep in the information age, and openness is a safer strategy. The tendency to classify everything means that the NSA won’t be able to sort what really needs to remain secret from everything else. The younger generation is more used to radical transparency than secrecy, and is less invested in the national security state. And whistleblowing is the civil disobedience of our time.

At this point, the NSA has to assume that all of its operations will become public, probably sooner than it would like. It has to start taking that into account when weighing the costs and benefits of those operations. And it now has to be just as cautious about new eavesdropping operations as it is about using FOXACID exploits attacks against users.

This essay previously appeared in the Atlantic.

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Posted on October 9, 2013 at 6:28 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.