On Mon, Mar 31, 2014 at 02:45:47PM -0800, I wrote:
How?
How to fix it, you mean? Good question. Probably depends on your OS. If your OS doesn't let you change it and you can't patch it, I'm afraid you'd have to use another OS (or a newer version of the one you're using).
https://en.wikipedia.org/wiki/Idle_Scan says:
The latest versions of Linux, Solaris, OpenBSD, and Windows Vista are not suitable as zombie, since the IPID has been implemented with patches[4] that randomized the IP ID.[1]