Session Management Techniques to Prevent Session Identifier Theft via XSS Attacks

B.

The correct answer to the question is option E: Implementing session cookies with the HttpOnly flag.

Explanation: Session management is a critical aspect of web application security. It involves the creation, management, and destruction of user sessions. Sessions are created when a user logs into a web application and remains active until the user logs out or the session times out. Session management is vulnerable to various attacks, such as cross-site scripting (XSS), session hijacking, and session fixation.

XSS attacks are a common attack vector in session management. In an XSS attack, the attacker injects malicious code into a web page, which is executed by the user's browser. The malicious code can steal the user's session identifier and use it to impersonate the user.

To prevent session identifier theft via an XSS attack, it is necessary to implement session cookies with the HttpOnly flag. The HttpOnly flag is a security feature that instructs the browser to prevent client-side scripts from accessing the cookie. This means that even if an attacker manages to inject malicious code into a web page, they will not be able to steal the session identifier from the session cookie.

The other options are also essential techniques for secure session management, but they do not directly address the prevention of session identifier theft via an XSS attack. Ensuring the session identifier length is sufficient and creating proper session identifier entropy can help prevent session brute-forcing attacks. Applying a secure attribute on session cookies and utilizing transport layer encryption on all requests can help protect the confidentiality and integrity of session data, but they do not prevent session identifier theft via an XSS attack.

In conclusion, to prevent session identifier theft via an XSS attack, it is necessary to implement session cookies with the HttpOnly flag.