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I'm setting up a physically isolated Tor system (with one computer serving as the workstation and another as a Tor gateway), and I'm concerned about methods a worm could use to infect my OS. In the event that my workstation is compromised and attempts to attack the gateway, what kind of attacks could be attempted? Would something like a networking worm be able to bridge the 'air gap' between the two computers and compromise my identity, and would there be any benefit to using an Ethernet connection vs. WiFi between the two computers?

Sorry if I sound like an absolute newbie; I just read this document and was wondering how a virus could 'break out' of a physically isolated system.

http://www.invisiblethingslab.com/resources/2014/Software_compartmentalization_vs_physical_separation.pdf

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    "air gap" refers to a computer not on any network. I don't think that's what you are talking about. May 17, 2015 at 4:46

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Tor provides you anonymity, but it will not protect you at all from malwares or any other security threats. All recommendation regarding network security must therefore be scrupulously respected in order to ensure your network safety.

You do not mention it in your description, but be aware that your setup matches Whonix project, so if you do not want to reinvent the wheel and benefit from their experience feel free to rely on them for your setup.

At last, personally I would strongly recommend using an ethernet connection. Using a properly secured Wifi access should not be a major threat, so if it has a real benefit for you it may still be considered, but personally I would feel less comfortable in the idea of spreading confidential data everywhere around me, even in encrypted form.

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I'm setting up a physically isolated Tor system (with one computer serving as the workstation and another as a Tor gateway), ...

I don't know what your "physically isolated" refers to, but since you have a work station connected to a Tor gateway I would assume that you plan to use the workstation to access the internet through the Tor gateway. In this case you have no "physical" but only a (weak) logical separation.

In any case a common "worm" propagating through the network could usually already prevented if you don't offer any services on your system, that is you have only outgoing connections. But since you probably want to access the web and maybe read email you should worry less about hackers trying to attack your system from outside, but more about attacks you are implicitly inviting to your system, i.e. drive-by-downloads, malvertising, phishing mails with infected attachments etc. There is no absolute protection against this, but using a read-only system (like a Linux live-ISO distribution) can help, especially if you restart to get a clean version before doing any sensitive activities.

Would something like a networking worm be able to bridge the 'air gap' between the two computers and compromise my identity,

I think you confuse some concepts. "air gap" means that you have no connectivity between this systems, i.e. data transport has to be done manually with USB sticks etc. (W)LAN is not an air gap. And, to compromise your identity it is not necessary to compromise your Tor gateway, but a Cross-Site-Scripting attack against some vulnerable web application where you are logged in could be sufficient to forward your identity to a third party. There is a reason Tor browser has script disabled by default using NoScript, even if more and more sites don't work without Javascript.

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    I find the word "weak" a bit strong in this context. Indeed, having a dedicated physical computer serving as Tor Gateway seems to provide quite a strong guaranty that no traffic would leak out of the network without being tunneled. It is typically the setup proposed by Whonix, here in its hardware implementation (a logical one, less secure, also exists relying on the usage of two VMs). May 17, 2015 at 13:25
  • @WhiteWinterWolf: It does not matter much if the malware comes in through the Tor tunnel or outside of Tor. Just because t is encrypted does not mean that the data are safe, its only that the communication is protected against modification and sniffing (and some privacy due to onion routing). May 17, 2015 at 13:46
  • @SteffenUlrich: You are actually saying exactly what I'm saying in my own answer below, so I guess we agree on that ;). However, using a dedicated separated hardware running a potentially hardened system as a Gateway does not seem to fall in either the "logical" nor the "weak" classes for me, and seems strong for the pursued goal which is anonymity and preventing leaks caused by non-tunneled data. But we agree that this goal and setup does not include anything related to malware prevention or detection. May 17, 2015 at 14:00
  • @WhiteWinterWolf: I think we have basically the same view, which only differs what we consider weak :) But I still consider the isolation logical mostly, because it is only done by software. I view physical isolation as somewhing like unidirectional networks based on optical cabling where there is only a receiver on one side and thus traffic can only flow in one direction because of hardware and not because of software. May 17, 2015 at 14:10
  • @SteffenUlrich: I confirm Whonix doesn't require any soldering, so in this respect it would indeed fall in the "logical isolation" in your definition. I still remain a bit perplex since, for instance, there would be no hardware firewall at all according to this definition (I guess an hardware firewall would be something requiring to play with on-board jumpers to defines the rules), and just a minor difference between pure software firewall and dedicated firewall running embedded in a specific appliance which would both be only logical isolation. May 17, 2015 at 14:39

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