Enable/Disable Sharing (SSH/File) Based on Network? Is it possible to enable and disable the Sharing features (ssh, file sharing, etc) based on the current network?

For example, I want file sharing and SSH to be enabled on my trusted home network.  However, I don't want these enabled when I am connected to untrusted public networks.

Is it possible to set up this policy?  To differentiate between a home and public network?

I don't think this occurs by default because I often see shared folders and shared itunes libraries on public networks.  While they are protected by passwords, I would rather be completely sealed up on public networks.

Thanks!
You can use ControlPlane for this. It allows you to control your context, like home and other, and set actions for it: when 'enter' home context, enable file sharing, when 'leave' home context, disable file sharing.