It wouldn't take much shielding at all for this specific one... you could line a case with a faraday mesh material which would probably me enough for most similar attacks.

That said, for most of these kinds of things, you have to get a malicious payload on such a system. The stuxnet approach is one way, if you have specific targets. Aside from that, you pretty much need phyxical access and be able to load a malicious software. At that point, you may as well stick a small usb bluetooth/wireless dongle, depending on the situation... assuming it's a standard desktop, there's a good chance of unused USB 2 header you could piggy back on.

At that point, an actual faraday cage or mesh on the room in question would be the next practical vector. Some secure buildings are up to 6' thick walls, no communications out except through known devices on wired ports with software checking in place (seen this in finance).