The correct answer is 'A process of confirming user input conforms to the expected format and value ranges' because input validation involves checking the data provided by users against predetermined criteria to ensure it is properly formatted and within acceptable parameters. This is a security measure to prevent malicious or accidental input that could harm the system or lead to security vulnerabilities. The other answers describe aspects that are related to input validation but are not definitions of the concept itself. For example, 'Applying security patches' refers to updates that address vulnerabilities, which is part of maintaining a secure system but isn't directly related to handling user input. 'Encrypting data transmissions' involves securing data in transit, which is separate from validating the integrity of the input at the time of entry.