What would NOT be a reasonable defense against scanning vulnerabilities?

Changing the application banner is not a reasonable defense against scanning vulnerabilities because it merely alters the message or identifier of the application without addressing the underlying vulnerabilities. An application banner, often seen during the initial connection to a service or application, typically provides information about the application version and its capabilities.

While changing this banner may obscure information from potential attackers, it does not mitigate the risks or vulnerabilities present in the application itself. Attackers can still perform scans to identify security weaknesses regardless of the banner displayed. In contrast, patching vulnerabilities, implementing a firewall, and using an intrusion prevention system are active strategies designed to prevent unauthorized access and protect against exploitation, making them more effective in defending against vulnerabilities.