What feature can be enabled in CloudTrail to prevent log file tampering?

CloudTrail log file validation is an essential feature that ensures the integrity of log files by allowing users to verify whether the logs have been tampered with. When log file validation is enabled, CloudTrail generates a hash for each log file and stores it in a separate location. This allows administrators to perform a verification step to confirm that the logs remain unchanged. Since maintaining the authenticity of logs is crucial for compliance and security monitoring, this validation feature acts as a safeguard against unauthorized alterations.

By implementing log file validation, organizations can ensure that any tampering with the logs can be detected, which is vital for auditing and incident response. This capability stands out as a direct countermeasure against tampering, making it the correct answer in this context.

Other features like monitoring, alerts, and encryption serve different purposes: monitoring and alerts are used for real-time notifications and responses, while encryption focuses on securing the data at rest or in transit, but they do not specifically address the integrity checking of log files.