http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-August/010379.html
https://github.com/bitcoinxt/bitcoinxt/commit/73c9efe74c5cc8faea9c2b2c785a2f5b68aa4c23
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.
...