John, a professional hacker, targeted CyberSol Inc.

John, a professional hacker, targeted CyberSol Inc., an MNC. He decided to discover the loT devices connected in the target network that are using default credentials and are vulnerable to various hijacking attacks. For this purpose, he used an automated tool to scan the target network for specific types of loT devices and detect whether they are using the default, factory-set credentials. What is the tool employed by John in the above scenario?