When advising on protecting a session ID in a web application, what is a recommended practice?

Using a timestamp and client-identifying information as a recommended practice for protecting a session ID is effective for various reasons. Incorporating timestamps helps to track the validity of the session, ensuring that it remains active only for a predetermined duration. This reduces the risk of session hijacking and replay attacks, as an attacker would need not only to obtain the session ID but also to know the exact timing of the session's creation and its allowed duration.

Moreover, client-identifying information adds an additional layer of security. Associating the session ID with specific characteristics of the client, such as browser type, operating system, or attributes uniquely identifiable to the user, helps verify that the session requests are coming from the legitimate user. If a session ID is used from a different set of client-identifying information, it can be invalidated, thus enhancing protection against unauthorized access.

While other practices like using secure random number generators for session keys or regularly rotating session IDs are also important, they do not directly contribute to this aspect of protecting the session in the same manner. Implementing measures to bind session IDs with unique and verifiable client attributes, alongside time constraints, offers a robust method for maintaining session integrity and security in web applications.