What is input validation and why is it important for security and data integrity?

• A. Validate and sanitize inputs to prevent invalid or malicious data, reducing security risks and ensuring data integrity.
• B. Only check data types to improve performance.
• C. Validate inputs to improve performance.
• D. Validate inputs after processing to catch errors.

Answer: (C)

Input validation is checking data from any source before it enters your system, making sure it matches expected formats, types, lengths, and allowed values. Sanitizing is part of this process, cleaning the data to remove or neutralize dangerous content. This matters for security because untrusted input can carry attacks like SQL injection or cross-site scripting; validating and sanitizing stops many of these threats at the boundary. It also protects data integrity by ensuring only well-formed data is stored or acted upon, preventing corrupted or out-of-range values from causing errors or inconsistencies. The idea is to validate up front, before processing, so bad data can’t influence logic or storage. Validating after processing is too late, and focusing only on performance misses the larger benefits of security and data quality.