For this “controlled interruption” JAS recommends returning an address within the 127/8 loopback range: “Responding with an address inside 127/8 will likely interrupt any application depending on an NXDOMAIN or some other response, but importantly also prevents traffic from leaving the requestor’s network and blocks a malicious actor’s ability to intercede.”

Instead of the familiar 127.0.0.1 loopback address for localhost, the report suggests “127.0.53.53”. Because the result is so unusual, it’s likely to be flagged in logs and sysadmins who aren’t aware of a name collision issue are likely to search online for information about the address problems.

via ICANN seeks to tackle DNS namespace collision risks – ICANN, Internet Corporation for Assigned Names and Numbers, gTLD, security, domain names – Computerworld.