Little Snitch 2.4.2
Well not the latest version which iCloud ready. but still the best firewall app for your mac, not tested by me, since i use my own license for this handy app. this one include serial, let me know if this still working, in case to prevent blacklist, try this old guide
A firewall protects your computer against unwanted guests from the Internet. But who protects your private data from being sent out? Little Snitch does!
Little Snitch 2.4.2 - August 8, 2011
Improves OS X Lion compatibility.
Fixes a kernel panic.