Certificate Proxy Attack

C.

The correct answer is C. Man-in-the-middle.

Explanation: A secure website uses SSL/TLS certificates to establish a secure connection between the web server and the user's browser. When a user accesses a secure website, the web server presents its SSL/TLS certificate to the user's browser to establish a secure connection. The user's browser verifies the authenticity of the certificate by checking the certificate chain and confirming that the certificate is signed by a trusted certificate authority (CA).

In this scenario, the network administrator has noticed that the web gateway proxy on the local network has signed all of the certificates on the local machine. This means that the proxy has been configured to intercept the SSL/TLS traffic between the user's browser and the web server and to replace the web server's SSL/TLS certificate with its own certificate. The proxy then signs its own certificate with its own CA, making it appear as if the proxy is the legitimate certificate authority for the website.

This is a classic example of a man-in-the-middle (MITM) attack. In a MITM attack, the attacker intercepts the communication between two parties and can modify or steal the data being exchanged. In this case, the web gateway proxy is performing a MITM attack by intercepting the SSL/TLS traffic and replacing the legitimate certificate with its own certificate. This allows the proxy to decrypt and inspect the traffic before forwarding it to the user's browser.

While this may be a legitimate configuration for certain security purposes such as content filtering or malware inspection, it can also be abused by attackers who can use the same technique to intercept sensitive information such as login credentials, credit card numbers, or other sensitive data being exchanged over the secure connection.

Therefore, the correct answer is C. Man-in-the-middle.