Mike Perry recently discovered a leak bug in custom transparent proxies (not related to Whonix!) and published his findings on the tor-talk mailing list:
This leak test has been adapted for Whonix and documented here:
Fortunately, I wasn’t able to reproduce this leak using Whonix. Probably because the Linux version Whonix is using isn’t affected by this bug and/or because Whonix’s Firewall uses iptables default policy drop for input-, output-, fowardchain and only allows the Tor user to establish external connections. However, other users using different host operating systems and setups than I should repeat the test.
Please feel encouraged,
– to comprehend the original thread on the tor-talk mailing list
– verify yourself that this leak test doesn’t find a leak and share your results
– check if upstream (Linux kernel / iptables) consider this a bug and if it has already been reported (this is not clear yet)