A Computer Hacking Forensic Investigator (CHFI) is trying to identify a hidden data leak happening through seemingly benign PDF documents sent from a corporate network. While examining a suspicious PDF, he discovers a series of unexpected objects in the file’s body. Given the following hex signatures of various file formats: JPEG (0xffd8), BMP (0x424d), GIF (0x474946), and PNG (0x89504e), which of the following actions should he take next?
The correct action for a Computer Hacking Forensic Investigator is to examine the cross-reference table (xref table) for any unusual links to objects. This table contains entries that describe the byte offset of each object within the PDF file. Checking the xref table for anomalies or unexpected objects would help the investigator identify hidden or suspicious data embedded within the PDF. This approach is more aligned with forensic investigation practices for dissecting and analyzing the internal structure and contents of a PDF file.
The first bits of a file represent the file type, and JPEG files start with the binary value 0xffd8 (start of image; SOI) and end with the binary value 0xffd9 (end of image; EOI). Therefore, ffd8 (the 0x is implied) at the beginning represents a JPEG file when viewed with a hex editor.
In the scenario where a Computer Hacking Forensic Investigator (CHFI) is examining a suspicious PDF document for hidden data leaks and has discovered unexpected objects in the file’s body, the most appropriate next step would be: C. Examine the cross-reference table (xref table) for any unusual links to objects Explanation: The cross-reference table (xref table) in a PDF file contains references to all the objects within the PDF, inclu ding their locations. Examining the xref table can help identify any unusual or unexpected links to embedded objects, which may indicate hidden data or steganographic techniques being used to leak information.