OS X firewall blocking torrents outside of VPN I've seen plenty of tutorials for this around for Windows but I'm wanting to do it on OS X Yosemite. Is it possible to configure the firewall such that torrent traffic will only ever be permitted when I'm a connected to a VPN?
Yes it is possible, you can create a blocking rule using pf, that only allows traffic on the the port your torrent software is using, to/from the virtual interface created by the VPN. Take a look at a cheat sheet for pf for ideas. Or if you prefer a GUI you might check out icefloor.