01 - Digital Forensics

Methodology

1. Collection: The first phase of digital forensics is data collection. Identifying all the devices from which the data can be collected is essential. Usually, an investigator can find personal computers, laptops, digital cameras, USBs, etc., on the crime scene. It is also necessary to ensure the original data is not tampered with while collecting the evidence and to maintain a proper document containing the collected items’ details. We will also be discussing the evidence-acquisition procedures in the upcoming tasks.
2. Examination: The collected data may overwhelm investigators due to its size. This data usually needs to be filtered, and the data of interest needs to be extracted. For example, as an investigator, you collected all the media files from a digital camera on the crime scene. You may only require some of the media as you are concerned with the media recorded on a specific date and time. So, in the examination phase, you would filter the media files of the required time and move them to the next phase. Similarly, you may only need the data of a specific user from a system containing numerous user accounts. The examination phase helps you filter this particular data for analysis.
3. Analysis: This is a critical phase. The investigators now have to analyze the data by correlating it with multiple pieces of evidence to draw conclusions. The analysis depends upon the case scenario and available data. The analysis aims to extract the activities relevant to the case chronologically.
4. Reporting: In the last phase of digital forensics, a detailed report is prepared. This report contains the investigation’s methodology and detailed findings from the collected evidence. It may also contain recommendations. This report is presented to law enforcement and executive management. It is important to include executive summaries as part of the report, considering the level of understanding of all the receiving parties.

• Computer forensics: The most common type of digital forensics is computer forensics, which concerns investigating computers, the devices most commonly used in crimes.
• Mobile forensics: Mobile forensics involves investigating mobile devices and extracting evidence such as call records, text messages, GPS locations, and more.
• Network forensics: This area of forensics covers investigation beyond individual devices. It includes the whole network. The majority of the evidence found in networks is the network traffic logs.
• Database forensics: Many critical data is stored in dedicated databases. Database forensics investigates any intrusion into these databases that results in data modification or exfiltration.
• Cloud forensics: Cloud forensics is the type of forensics that involves investigating data stored on cloud infrastructure. This type of forensics sometimes gets tricky for the investigators as there is little evidence on cloud infrastructures.
• Email forensics: Email, the most common communication method between professionals, has become an important part of digital forensics. Emails are investigated to determine whether they are part of phishing or fraudulent campaigns.

Proper Authorization

The forensics team should obtain authorization from the relevant authorities before collecting any data. Evidence collected without prior approval may be deemed inadmissible in court. Forensic evidence contains private and sensitive data of an organization or individual. Proper authorization before collecting this data is essential for investigating according to the limits of the law.

Chain of Custody

Imagine that a team of investigators collects all the evidence from the crime scene, and some of the evidence goes missing after a few days, or there is any change in the evidence. No individual can be held accountable in this scenario because there is no proper process for documenting the evidence owners. This problem can be solved by maintaining a chain of custody document. A chain of custody is a formal document containing all the details of the evidence. Some of the key details are listed below:

• Description of the evidence (name, type).
• Name of individuals who collected the evidence.
• Date and time of evidence collection.
• Storage location of each piece of evidence.
• Access times and the individual record who accessed the evidence.

This creates a proper trail of evidence and helps preserve it. The chain of custody document can be used to prove the integrity and reliability of the evidence admitted in court. A sample chain of custody can be downloaded from  here .

Use of Write Blockers

Write blockers are an essential part of the digital forensics team’s toolbox. Suppose you are collecting evidence from a suspect’s hard drive and attaching the hard drive to the forensic workstation. While the collection occurs, some background tasks in the forensic workstation may alter the timestamps of the files on the hard drive. This can cause hindrances during the analysis, ultimately producing incorrect results. Suppose the data was collected from the hard drive using a write blocker instead in the same scenario. This time, the suspect’s hard drive would remain in its original state as the write blocker can block any evidence alteration actions.

Windows Forensics

As part of the data collection phase, forensic images of the Windows operating system are taken. These forensic images are bit-by-bit copies of the whole operating system. Two different categories of forensic images are taken from a Windows operating system.

• Disk image: The disk image contains all the data present on the storage device of the system (HDD, SSD, etc.). This data is non-volatile, meaning that the disk data would survive even after a restart of the operating system. For example, all the files like media, documents, internet browsing history, and more.

• Memory image: The memory image contains the data inside the operating system’s RAM. This memory is volatile, meaning the data will get lost after the system is powered off or restarted. For example, to capture open files, running processes, current network connections, etc., the memory image should be prioritized and taken first from the suspect’s operating system; otherwise, any restart or shutdown of the system would result in all the volatile data getting deleted. While carrying out digital forensics on a Windows operating system, disk and memory images are very important to collect.

Let’s discuss some popular tools used for disk and memory image acquisition and analysis of the Windows operating system.

FTK Imager: FTK Imager is a widely used tool for taking disk images of Windows operating systems. It offers a user-friendly graphical interface for creating the image in various formats. This tool can also analyze the contents of a disk image. It can be used for both acquisition and analysis purposes.

Autopsy:  Autopsy  is a popular open-source digital forensics platform. An investigator can import an acquired disk image into this tool, and the tool will conduct an extensive analysis of the image. It offers various features during image analysis, including keyword search, deleted file recovery, file metadata, extension mismatch detection, and many more.

DumpIt:  DumpIt  offers the utility of taking a memory image from a Windows operating system. This tool creates memory images using a command-line interface and a few commands. The memory image can also be taken in different formats.

Volatility:  Volatility  is a powerful open-source tool for analyzing memory images. It offers some extremely useful plugins. Each artifact can be analyzed using a specific plugin. This tool supports various operating systems, including Windows, Linux, macOS, and Android.

Note: Various other tools are also used to acquire and analyze disk and memory images of the Windows operating system.