You've probably figured this out by now, but I'm pretty sure you're missing the point. From your other comments in this thread you appear to think that the mach

You've probably figured this out by now, but I'm pretty sure you're missing the point. From your other comments in this thread you appear to think that the machine needs to be internet-accessible. Have a public IP. Open Firewall. All that. The reason this is so dangerous is that it needs none of that. All it needs is for your development machine to have access to the internet. I open up a project, enable this, and run rackup locally. I then view your Twitter stream, where you've embedded a crafted link behind a URL shortener. Because that link is executed by me, you've now remotely executed code on my machine. Assuming I'm anything like most Rails shops you can probably get to a number of other machines through my machine.