Probable Cause: TLS Configuration with AES-GCM-256, SHA-384, and ECDSA

D.

The given configuration of the web server indicates that it is using strong cryptographic algorithms for data encryption, integrity, and authentication. AES-GCM-256 is a widely accepted symmetric encryption algorithm that offers a high level of security and efficiency. SHA-384 is a robust hashing algorithm that provides a high level of integrity protection to the data. ECDSA is a widely used digital signature algorithm that provides authentication and non-repudiation capabilities.

Considering the above information, it is less likely that the information loss breach occurred due to the insufficient key bit length. The given cipher suite and encryption method are strong enough to provide adequate security for the data in transit. However, it is still essential to use sufficiently long keys to prevent brute-force attacks.

Weak cipher suites can be exploited by attackers to decrypt the intercepted data. However, the given cipher suite is strong and not susceptible to known attacks. Therefore, it is less likely that the information loss breach occurred due to a weak cipher suite.

Unauthenticated encryption methods can lead to data loss breaches as they provide no guarantee that the data has not been tampered with. However, the given cipher suite and encryption method provide authentication and integrity protection for the data. Therefore, it is less likely that the information loss breach occurred due to unauthenticated encryption.

Poor implementation can lead to information loss breaches, regardless of the strength of the cryptographic algorithms used. A poorly implemented web server can have vulnerabilities that can be exploited by attackers to gain unauthorized access to the data. Therefore, it is most likely that the information loss breach occurred due to a poor implementation of the web server.

In conclusion, the most likely cause of the information loss breach in the given scenario is a poor implementation of the web server.