I keep a terminal window open with nettop running in it. Yesterday I upgraded to TorBrowser 3.6 and today I just noticed in nettop that an instace of Python runs along side TorBrowser with active sockects (not sure if that the correct term) to the Tor netowrk.

The previous version didn't have Python appear in nettop.

I am also helping to trouble shoot an open source DNS app. I have run a couple of commands in the Terminal and I'm not 100% sure if they didn't cause the instance of Python to appear.

Can an OS X user confirm if nettop also displays python while they run TorBrowser. Thaks

I did some testing and it seems to be related to the new obfs3 bridges feature in v3.6 of TorBrowser.

When My Internet Service Provider (ISP) blocks connections to the Tor network is selected in Tor Network Settings (Connect with provided bridges obfs3 was left as default) the Python instance appears in nettop. If that option is deselected then no Python.

That would explain why it wasn't there in the previous ver - the obfs3 bridge feature is new to 3.6.

I'm 99% satisfied that its kosher but if any one would like to confirm it that would be great.

1 Answer 1


Yes. You are correct in your understanding that using an obfs3 bridge will cause a python interpreter to be spawned. Currently all the pluggable transport types distributed along the Tor Browser use python, though that's not guaranteed to remain the case in the future (meek using Go is an example of something in development that explicitly does not use python).

If you're curious you could look in Tor/PluggableTransports and see all the scripts, or look at the relevant PT's source code in the various source repositories.

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