Apple - iPod Reverse Tethering via USB
From all my research your request is not possible. Only wireless via internet sharing on your windows 7 machine or the mac.
Apparently this is possible, if your iPhone is jailbroken:
(update: this does not seem to work for iPod touch, iPads without 3g etc. - because they lack the "second network card" interface)
can i get it on my ipod touch...? Unfortunately, not. ipod touch doesn't have gprs/edge network interface to redirect it to the proxy.
Follow this lengthy procedure (note that it's originally for iOS 2.x, using a Windows PC):
SSH to get your iphone online via USB cable
We will connect it to the Internet-connected PC via standard USB cable and get the iphone online in this passthru, reverse mode. Without wifi, without GPRS/EDGE fee to GSM operator. Incredible, impossible? Read further...
- On the PC you will need: Bitvise Tunnelier, itunnel
- And on the iPhone/iPad3G: OpenSSH and a proxy-setting file
Alternatively you could try this procedure by dy2k (again only for iDevices supporting Internet Tethering) :
Reverse Tethering iPhone 3G/3Gs using USB
Step 1: Set up internet tethering on your iPhone.
Step 2: Plug you iPhone into your PC using the provided USB cable.
Step 3: Go to Settings>General>Network>Internet Tethering and switch it to "On." Then it will prompt you for bluetooth or USB, select USB
Step 4: Go to network connections and you should see your LAN connection and a new connection that says "Apple Mobile Device Ethernet." Simply highlight both connections, right click on one and select "Bridge."
You will now be using your PC's internet connection on your iPhone! It works for Cydia App store, Facebook, Safari, ect ect.
Note: After terminating the connection you must delete the bridge and make a new one when you re-connect.