In a forensic ISO image, which artifact is most likely to indicate the source medium type?

• A. Disc descriptor in the ISO9660 volume descriptor
• B. NTFS file creation times
• C. Master Boot Record on the host disk
• D. Slack space on a FAT32 partition

Answer: (A)

In an ISO 9660 image, the metadata stored in the volume descriptors describes the disc as it was created, including information about the medium. The disc descriptor within the ISO9660 volume descriptor directly encodes the type of medium (for example, CD-ROM, CD-R, DVD-ROM) and related characteristics. This makes it the most reliable artifact for inferring the source medium type when analyzing the image, because it is specifically designed to capture the nature of the physical disc that was used.

Other artifacts don’t serve this purpose as directly. NTFS file creation times pertain to a Windows file system and may not even be present in a standard ISO9660 image. The Master Boot Record on the host disk is outside the ISO image itself, so it won’t reveal the image’s source medium. Slack space on a FAT32 partition relates to a particular partition’s unused space and isn’t indicative of the medium that produced the ISO.