Whonow is a malicious DNS server designed to execute DNS Rebinding attacks in real-time. The tool operates as a specialized DNS server that facilitates DNS rebinding attacks by manipulating DNS responses to bypass same-origin policy restrictions in web browsers. DNS rebinding attacks allow attackers to access internal network resources and services that would normally be protected by network boundaries. The server can be deployed to respond to DNS queries with crafted responses that enable the rebinding attack vector. This technique is commonly used in penetration testing and security research to demonstrate vulnerabilities in network configurations and web application security models. A public instance of the tool is available at rebind.network:53 for testing and demonstration purposes. The tool provides an on-demand approach to DNS rebinding, allowing security professionals to execute these attacks without requiring extensive setup or configuration.