On Mon, Oct 7, 2013 at 5:16 PM, Eugen Leitl <[1]eugen@leitl.org> wrote: [2]http://www.wired.com/opinion/2013/10/149481/ Want to Evade NSA Spying? Dont Connect to the Internet BY BRUCE SCHNEIER 10.07.13 6:30 AM Photo: Ariel Zambelich / WIRED; Illustration: Ross Patton / WIRED Since I started working with Snowdens 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 theyre 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 thats 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, theres the potential for attack. And air gaps have been breached. Stuxnet was a U.S. 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 U.S. military networks. These attacks work by exploiting security vulnerabilities in the removable media used to transfer files on and off the air gapped computers. Bruce Schneier is a security technologist and author. His latest book is Liars and Outliers: Enabling the Trust Society Needs to Survive. Since working with Snowdens 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. Its 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 friends 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 wont 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. Thats all. (No, I dont have any inside knowledge about TrueCrypt, and theres a lot about it that makes me suspicious. But for Windows full-disk encryption its that, Microsofts BitLocker, or Symantecs PGPDisk and I am more worried about large U.S. 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 doesnt 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 its an attempt to make it harder for the attacker to target your computer. 5. Turn off all auto-run features. This should be standard practice for all the computers you own, but its especially important for an air-gapped computer. Agent.btz used autorun to infect U.S. 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. Dont 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. Youre 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 dont 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 cant 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 youve 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; Ive 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 cant 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 youll be moving public files and it wont matter, but sometimes you wont be, and it will. And if youre using optical media, those disks will be impossible to erase. Strong encryption solves these problems. And dont forget to encrypt the computer as well; whole-disk encryption is the best. One thing I didnt do, although its 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 its probably impossible to enforce for any network more complicated than a single computer with a single user. But if youre thinking about setting up an air-gapped computer, you already believe that some very powerful attackers are after you personally. If youre 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 thats too much paranoia for me right now. I like Bruce much, i have read all of him, every book, mostly article, from years. Butno normal person would follow these advice,all smartphones should be turned off, each tablet, and every pc should be turned in a anonyomous client of an anonymous network. Sure, who believe in the paranoia model definitely find comfort in these indications, for example i am one. But those who follow this model, really, are following it also not in only the cyberspace, but also in the real life, every day ? Really? Internet is perhaps evil but perhaps also our world is not so a sane and secure place, sometime (or every time, depend). Best References 1. mailto:eugen@leitl.org 2. http://www.wired.com/opinion/2013/10/149481/