What method adds a layer of security over existing applications on a device?

Application wrapping is a security technique that enhances the protection of existing applications on a device. This method involves the process of wrapping applications in a container that provides an additional layer of security features. For instance, application wrapping can enforce security policies such as authentication requirements, data encryption, and access controls, which help safeguard sensitive information and mitigate risks related to unauthorized access.

By utilizing application wrapping, organizations can deploy security measures that are not originally built into the app, allowing for better protection against threats such as data breaches or unauthorized data sharing. It effectively creates a controlled environment for the application to operate in, ensuring that even if the app itself is compromised, the security framework in place will help contain the damage.

While other options like a VPN and user authentication provide important security features, they do not specifically enhance existing applications directly in the way application wrapping does. Code obfuscation is related to protecting the code itself from being understood or reverse-engineered but does not provide operational security enhancements for the application in the same manner. Thus, application wrapping stands out as the best choice for adding security layers over existing applications on a device.