To prevent poaching of an Internet Protocol (IP) set top box (STB) asset or similar network computing device from one system operator to another, code executing in the IP STB not only authenticates downloaded software images using a public key provided in a serial-number assigned digital certificate, but also confirms that the serial number appears on a signed whitelist, or does not appear on a signed blacklist. The code executing in the STB further preferably enforces a rule that only the authority that signed the already-loaded whitelist/blacklist may replace it with a new list. Such a "sticky whitelist/blacklist" ensures that if the STB boots or resets in a new network, the existing authentication list will not be replaced by a list that is valid for a new or different network, and, as a result, that new software code images will not be authenticated.