[bitcoin-dev] Bitcoin XTs Tor IP blacklist downloading system has significant privacy leaks.

Andrew LeCody andrewlecody at gmail.com
Tue Aug 18 23:56:51 UTC 2015

This should probably be posted on the BitcoinXT mailing-list, as Bitcoin
Core does not currently include this feature.

On Tue, Aug 18, 2015 at 6:36 PM F L via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> wrote:

> Bitcoin XT contains an unmentioned addition which periodically downloads
> lists of Tor IP addresses for blacklisting, this has considerable privacy
> implications for hapless users which are being prompted to use the
> software.  The feature is not clearly described, is enabled by default, and
> has a switch name which intentionally downplays what it is doing
> (disableipprio).  Furthermore these claimed anti-DoS measures are trivially
> bypassed and so offer absolutely no protection whatsoever.
> Connections are made over clearnet even when using a proxy or onlynet=tor,
> which leaks connections on the P2P network with the real location of the
> node.  Knowledge of this traffic along with uptime metrics from
> bitnodes.io can allow observers to easily correlate the location and
> identity of persons running Bitcoin nodes.  Denial of service can also be
> used to crash and force a restart of an interesting node, which will cause
> them to make a new request to the blacklist endpoint via the clearnet on
> relaunch at the same time their P2P connections are made through a proxy.
> Requests to the blacklisting URL also use a custom Bitcoin XT user agent
> which makes users distinct from other internet traffic if you have access
> to the endpoints logs.
> https://github.com/bitcoinxt/bitcoinxt/commit/73c9efe74c5cc8faea9c2b2c785a2f5b68aa4c23
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