Forensics is the application of science to investigate crimes and establish facts. With the use and spread of digital systems, such as computers and smartphones, a new branch of forensics was born to investigate related crimes: computer forensics, which later evolved into, digital forensics.
Think about the following scenario. The law enforcement agents arrive at a crime scene; however, part of this crime scene includes digital devices and media. Digital devices include desktop computers, laptops, digital cameras, music players, and smartphones, to name a few. Digital media includes CDs, DVDs, USB flash memory drives, and external storage. A few questions arise:
How should the police collect digital evidence, such as smartphones and laptops? What are the procedures to follow if the computer and smartphone are running?
How to transfer the digital evidence? Are there certain best practices to follow when moving computers, for instance?
How to analyze the collected digital evidence? Personal device storage ranges between tens of gigabytes to several terabytes; how can this be analyzed?
As a digital forensics investigator, you arrive at a scene similar to the one shown in the image above. What should you do as a digital forensics investigator? After getting the proper legal authorization, the basic plan goes as follows:
Acquire the evidence: Collect the digital devices such as laptops, storage devices, and digital cameras. (Note that laptops and computers require special handling if they are turned on; however, this is outside the scope of this room.)
Establish a chain of custody: Fill out the related form appropriately (Sample form). The purpose is to ensure that only the authorized investigators had access to the evidence and no one could have tampered with it.
Place the evidence in a secure container: You want to ensure that the evidence does not get damaged. In the case of smartphones, you want to ensure that they cannot access the network, so they don’t get wiped remotely.
Transport the evidence to your digital forensics lab.
At the lab, the process goes as follows:
Retrieve the digital evidence from the secure container.
Create a forensic copy of the evidence: The forensic copy requires advanced software to avoid modifying the original data.
Return the digital evidence to the secure container: You will be working on the copy. If you damage the copy, you can always create a new one.
Start processing the copy on your forensics workstation.
The above steps have been adapted from Guide to Computer Forensics and Investigations, 6th Edition.
When you create a text file, TXT, some metadata gets saved by the Operating System, such as file creation date and last modification date. However, much information gets kept within the file’s metadata when you use a more advanced editor, such as MS Word. There are various ways to read the file metadata; you might open them within their official viewer/editor or use a suitable forensic tool. Note that exporting the file to other formats, such as PDF, would maintain most of the metadata of the original document, depending on the PDF writer used.
Let’s see what we can learn from the PDF file. We can try to read the metadata using the program pdfinfo. Pdfinfo displays various metadata related to a PDF file, such as title, subject, author, creator, and creation date. (The AttackBox already has pdfinfo installed; however, if you are using Kali Linux and don’t have pdfinfo installed, you can install it using sudo apt install poppler-utils.) Consider the following example of using pdfinfo DOCUMENT.pdf.