What kind of analysis can reveal data hidden within legitimate file types?

File signature analysis is the correct choice because it involves examining the characteristics of files to determine their true type based on their content, rather than relying solely on the file extension associated with it. This analysis looks for specific patterns or signatures within the file that indicate what type of content it actually contains, which can be different from the file's name or extension.

In situations where data is concealed within legitimate file types, such as hiding malicious code within an image or document file, file signature analysis can uncover this hidden data. By accurately identifying these signatures, forensic analysts can recognize anomalies and potentially malicious content within files that appear normal at first glance.

The other approaches, while useful in different contexts, do not specifically focus on uncovering data hidden within legitimate file types. For instance, file hash analysis is primarily used for verifying file integrity and checking for duplicates, file content search pertains to keywords or specific data within files, and data duplication analysis focuses on identifying identical files to reduce storage or improve efficiency. These methods do not inherently reveal hidden data as effectively as file signature analysis does.