[tor-bugs] #5028 [Ooni]: Tor bridge scanning

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#5028: Tor bridge scanning
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 Reporter:  hellais  |          Owner:  runa                     
     Type:  project  |         Status:  assigned                 
 Priority:  normal   |      Milestone:  Sponsor F: March 15, 2012
Component:  Ooni     |        Version:                           
 Keywords:           |         Parent:                           
   Points:           |   Actualpoints:                           
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Comment(by karsten):

 We ran the first scans from a node in .cn today.  The scan had two phases:
 first, we scanned 20 bridges twice with a delay of one hour to see whether
 scanning affects bridge reachability in any way; second, we scanned 100
 bridges (10 of which were already contained in the previous phase) to have
 a larger sample.  All bridges were taken from the HTTPS bucket.

 In the first phase, only 2 out of 20 bridges were found as reachable.  One
 hour later, the same 2 bridges and another bridge were found as reachable.
 We concluded that the scan didn't lead to bridges being blocked and
 continued with the second phase.

 In the second phase, 14 out of 100 bridges were found as reachable.  From
 the 86 unreachable bridges we removed 6 bridges that were not found as
 reachable by Tonga, either.  That leaves us with 80 bridges that Tonga
 found to be running and the scan found to be unreachable.  Reasons for
 bridges being unreachable were: 77 x connection timed out, 1 x connection
 refused, and 2 x no route to host.

 A manual analysis of the bridge usage statistics reported by the 14
 reachable bridges confirms that these bridges are actually reachable from
 .cn: 1 bridge reported 24 connections from .cn, 5 bridges reported 16
 connections, 6 bridges reported 8 connections, and 2 bridges didn't report
 country statistics.  The bridge usage statistics reported by the 80
 presumably blocked bridges have not been analyzed.

 What else should we look at in the results?

 And what are the next steps towards "some sort of automated ground truth
 of bridge reachability from some countries" that we can take in, say, the
 next week?

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5028#comment:45>
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