How do I check if ICS is active and if so, how do I disable it?
Essentially, ICS is used when one computer on a network is the computer that actually has Internet access--usually over a modem.
ICS is used by that computer to share it's internet access with other computers on the network. It's usually used by dial-up accounts.
If you do not have your home computers set up in the above configuration, don't worry about it.