[ooni-dev] Complete list of Tor blocking events

Arturo Filastò art at torproject.org
Fri Sep 26 08:07:01 UTC 2014

On 9/25/14, 9:47 PM, Sadia Afroz wrote:
> Hi all,
> I am trying find a list of events when different countries blocked Tor
> to understand why and how those countries blocked it and how Tor
> resolved those issues. Do you know if anybody is maintaining such a list?
> I found censorshipwiki
> (https://trac.torproject.org/projects/tor/wiki/doc/OONI/censorshipwiki)
> that has a similar list. But it seems that it's not maintained any more
> as it doesn't have the recent blocking incident by Iran. Also I'm not
> sure how comprehensive is this list as it's missing Tunisia. 

Hi Sadia,

Yes you are right, that list is not much up to date. For some other,
also not much up to date, information you may also want to look at:


It contains packet dumps blocked in ethiopia and kazakhstan.

> Do you have any suggestion on how to create a comprehensive list of Tor
> blocking by countries? 
> My colleagues and I were thinking of two ways to go about this:
> 1. Get the total number of Tor users from every countries over time and
> look for anomalous fluctuations. When we created such a graph we noticed
> that huge number of bot controlled nodes that appear in almost every
> country's graph. It seems hard to identify real censorship events from
> graphs like this that can be affected by other events unrelated to
> censorship.

On this topic you may be interested in reading this paper:

It explains a method for detecting censorship of Tor based on metrics.
At the time of writing it though, we didn't have the botnet problem, so
I see how it can be a bit more complicated to do now.

> 2. Search for tickets on https://trac.torproject.org/projects/tor
> <https://trac.torproject.org/projects/tor/ticket/12727> with keywords
> related to censorship, for example "censorship", "block", "dpi". This
> has the potential problem of missing many events where nobody complained
> or filed a bug report with different keywords.
> Let me know if there are other places I should look into to find
> censorship events.

I am adding also Philip Winter to cc that may know of other resources to
use to get good data on censorship events related to Tor.

~ Art.

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