Hash Value Change Detection Methods

E.

Based on the scenario provided, the most likely method that has been used is A. Cryptography.

Cryptography is the practice of securing communication from third-party access or manipulation. Hashing is one of the cryptographic techniques used to verify the integrity of a file. It generates a unique digital fingerprint of a file that cannot be reversed to the original data, making it almost impossible to manipulate or alter the data. The slightest change in the file content will result in a different hash value. Hence, comparing hash values is an efficient way to detect any tampering with data.

In this case, the administrator received an alert from an application designed to check the integrity of the company's website. This application has most likely been designed to monitor the hash value of the media files present on the website. The alert indicates that the hash value for a particular MPEG file has changed, which could be an indication that the file has been tampered with or replaced with a different file.

However, upon further investigation, the media appears to be the same as it was before the alert. This suggests that the attacker has used a technique known as hash collision to modify the file without changing its content. Hash collision is a situation where two different sets of data generate the same hash value. Attackers can use this technique to manipulate the file without changing its content to avoid detection.

In conclusion, based on the scenario provided, the most likely method used by the attacker is Cryptography. The attacker has manipulated the file without changing its content by using hash collision.