Windows DRM Files Used to Decloak Tor Browser Users

Windows DRM Files Used to Decloak Tor Browser Users(bleepingcomputer.com)

79 points by edgarvm 9 years ago | 32 comments

throwaway2016a 9 years ago |

I only ever use Tor for security research and with the nature of my particular work, I don't have a reason to download files but...

If I did and I cared about anonymity I would never download a file unless all internet on my machine or VM was piped through Tor (such as using Whonix or some dedicated security appliance). If I was using the Tor browser I wouldn't even even turn on Javascript without those protections for that matter.

On the other side of the spectrum, running Tor on Windows is insane. Almost every flaw I have seen in Tor mostly or only effects Windows users.

throwaway7767 9 years ago |

The list of file formats that can trigger the viewer to fetch a resource over the internet is so large that it's impossible to cover them all. Unless you're working with plain text or something you know is safe, don't open files downloaded over Tor if you're running on a standard OS (and not, say, in a whonix workstation that's isolated from direct internet connections).

brudgers 9 years ago |

Tor was developed by the US Naval Research Laboratory as a munition (that's the strong view of cryptography and developing munitions is what NRL does). There are a number of assumptions baked into it's design. Among them is hygiene appropriate when handling munitions in the external operating environment.

Viewed as a munition, the fact that Tor source code was opened up more than a decade ago but well into the post-Patriot act era suggests that its direct value as a munition had become less significant. However, since the release seems to have had the effect of retarding development of alternatives for some years, this might be seen as an indirect value of Tor as a munition.

Practically speaking, Tor on its own and absent an ecosystem of serious security hygiene, is likely to leak data to an attacker with targeted intelligence and barely non-trivial technical means. Because relatively few people have the will and the technical skill and the need to do all the other things that are required to use Tor in a secure manner.

Or to put it another way, in the context of the GWOT, it seems likely to me that Naval Research Labs only provided a free and unlimited crytpographic munition only because it could readily defeat its use by adversaries.

cnvogel 9 years ago |

What's the standard way to use Tor for people who are really diligent with their operational security?

Personally I haven't used Tor except for short casual testing. But if my personal security would depend on the anonymity provided by Tor, I think I'd seriously consider adding an additional layer of protection to avoid information leaking out "to the sides".

mikegerwitz 9 years ago | |

Use Tails or Whonix which prevents leaking data outside of the Tor network. Qubes OS makes Whonix easy/transparent (though I haven't had the pleasure of trying out Qubes yet).

Never access files downloaded over Tor outside of those environments, and _never_ mix identities: if you're going to be pseudononymous, don't access files downloaded under another pseudonym or visit websites you'd access (especially if logging in) under another. If you're going to be anonymous, don't save the data: let it be ephemeral, which is easy in the case of Tails, which is ephemeral by default.

Always use Tor Browser, not Tor over Foxyproxy in a vanilla Firefox or something. Don't rely on torify on your normal setup for complete anonymity, for reasons above.

But it depends on your threat model. I _do_ do both things in the previous paragraph for my day-to-day stuff where my threat model involves e.g. advertisers and other privacy-invading trackers, where I'm reading tech-related articles or downloading videos of talks, for example. But that involves a number of other addons as well (e.g. Privacy Badger, HTTPS Everywhere, NoScript, uBlock Origin, self-destructing coookies, ...).

Edit: Forgot to mention: https://www.whonix.org/wiki/DoNot

ryanlol 9 years ago | | |

>Use Tails or Whonix which prevents leaking data outside of the Tor network. Qubes OS makes Whonix easy/transparent (though I haven't had the pleasure of trying out Qubes yet).

Use Whonix, not Tails. Tails doesn't do a particularly good job preventing leaks outside of Tor network.

dukeluke 9 years ago | | |

It's also a good idea to assume Tor is already pwned and to follow good opsec(burner devices, mac address cloaking, using open/pwned wifi APs, loading & running OS completely through ram, and use hard drive write blockers). True anonymity is tough nowadays.

kolme 9 years ago | |

Hardcore people in the security circles do all their serious stuff inside one-use-only virtual machines, once their stuff is done, the machine is deleted and shredded.

That's the most clean-cut way of not mixing anonymous and regular files/configurations/whatever.

If my life depended on Tor, I would definitely do this.

antocv 9 years ago | | |

Add to that - do not use full web-browsers, but curl/wget/links instead.

danjoc 9 years ago |

Not just windows DRM files. Specifying a special codec is enough to trigger an auto download attempt in certain players. You can even embed smil animations in quicktime files to trigger content downloads.

This is why the feds want to redistribute child porn for weeks at a time. They can't break tor to de-anonymize users. They need to distribute files with beacons in them for this plan to work. Never mind that the police have become the child porn traffickers.

http://disinfo.com/2016/01/why-did-the-fbi-operate-a-child-p...

UnoriginalGuy 9 years ago |

While true this is like any other file type that connects back to the internet. It has nothing at all to do with DRM in particular.

For example you could download a HTML file over Tor, that file could have a <img /> tag in it which reveals your real IP when you open it in the non-Tor browser. Ditto with Office macros, any scripting language, Adobe Reader, etc. If you're going to just accept through warning dialogs then you're in trouble.

hackerfantastic 9 years ago | |

There are other ways of doing a similar attack which have been covered by HD Moore. We found this one interesting due to the minimal interaction required on Windows and the prevalence of media sharing on the darknet (for good or evil).

hackerfantastic 9 years ago | | |

just to clarify, there are no warning messages doing this with signed WMV files. There is a single warning from Tor which you can selectively disable - and I am sure many users do. You open the file and the action is triggered, office documents now have protected mode which comes with alerting and I am sure that Adobe warns users in a similar fashion. Most users would not expect playing a movie file to perform this action hence why it has a use case here.

niij 9 years ago |

OFFTOPIC: Does anyone know the name of the song from that video? I searched for the title of what was playing, but only came up with some weird anime soundtracks for some reason.

campuscodi 9 years ago | |

Ask @hackerfantastic (Twitter). He made the video.

hackerfantastic 9 years ago | | |

It is a copyright free video from bassrebels.

youdontknowtho 9 years ago |

It would be interesting to see if this could be extended to images? Can't Windows DRM be used with certain image formats? It's just a thought.

ComodoHacker 9 years ago |

>such a niche attack

Niche indeed. The potential target group of users who think "just use Tor and you're safe" is vanishing rapidly.

nueded 9 years ago |

This is a TOR exploit in the same way that downloading a blob through TOR is a TOR exploit.

campuscodi 9 years ago | |

Nobody said it was a Tor exploit. It's just a deanonymization technique, which like most, rely on social engineering (convincing the user to push a "Save File" button).

kristofferR 9 years ago | | |

Would simply saving it, without opening it, execute it?