It is _not_ easy, or even possible, to "make up" an IP address that works for receiving data across the public Internet. The responses to packets you send from

It is _not_ easy, or even possible, to "make up" an IP address that works for receiving data across the public Internet. The responses to packets you send from such an address will not come back to you. This doesn't thwart all attacks (DNS query amplification, general flooding, etc), but their hack involved transmitting AND receiving data (ssh, http, etc). What is _easy_, however, is determining which country is using a given IP address. Particularly when the searching party is a superpower and the country they're investigating is known for having very few links to the Internet. And what connections they do have are severely restricted. I imagine it would be very difficult to find a reliable, exploitable proxy server inside North Korea that is accessible across the public Internet.