Forensic data recovery is the process of salvaging deleted, damaged, or otherwise inaccessible digital data for use as evidence in legal proceedings or criminal investigations.
It involves extracting data from digital devices like hard drives, smartphones, and other storage media. The goal is to recover files and information that may have been intentionally deleted or corrupted.
Forensic data recovery has become a crucial tool for law enforcement. As we continue to generate more digital data, investigators rely on recovering deleted emails, internet history, documents, photos, and other files to solve cases. According to one expert, digital evidence is used in virtually every criminal case today (Source).
The data recovery process involves multiple steps like imaging the drive, analyzing the data, bypassing passwords, recovering files, and validating the integrity of the information recovered. Proper handling of the storage devices and recovered data is critical to ensure it can be presented as credible evidence in court.
Planning the Recovery
The first step in forensic data recovery is to thoroughly assess the device that needs to be recovered. This involves documenting details about the device’s make, model, operating system, storage capacity, physical condition, and any indications of damage or tampering [1]. The examiner needs to understand how data is stored on that specific device in order to choose the proper recovery methods.
The next step is determining the scope and goals of the recovery. What specific files or data types need to be recovered? What time frame is relevant? Are deleted files needed or only existing ones? Understanding these parameters helps focus the recovery and analysis efforts.
With the device details and recovery goals defined, the examiner selects the appropriate tools and techniques. Software forensic tools like EnCase or FTK are commonly used to image storage media. Hardware write blockers [2] prevent altering the original data. The examiner may use file carving, data parsing, password cracking, or manual recovery methods depending on the device and data type. Multiple tools and techniques are often required for a thorough forensic data recovery.
Careful planning makes the difference between a successful recovery and an inadmissible or incomplete result. Documenting each step provides transparency and credibility to the process.
[1] https://www.altlaw.co.uk/blog/how-does-forensic-data-collection-work
[2] http://cybersecgroup.info/incident-response/computer-forensics/data-recovery-and-forensic-analysis
Imaging the Device
A key step in the forensic data recovery process is creating a bit-for-bit forensic image of the storage media. This involves making an exact copy of the data on the device, including both active files and deleted content. Best practices recommend using specialist hardware and software designed for digital forensic imaging. Common tools used include Tableau, Logicube Falcon, and AccessData FTK Imager.
When creating a forensic image, it is critical to use proper evidence handling techniques to maintain the integrity of the data. This includes documenting the process thoroughly with notes, photographs, and logs. The imaging process should happen in a controlled environment to avoid contamination. Encryption can complicate imaging, often requiring decryption prior to obtaining an accurate copy. Verifying the hash values of the original data and the image confirms it is an exact duplicate.
Following forensic imaging best practices preserves the evidentiary value of the data and ensures its admissibility in legal proceedings. This includes maintaining a chain of custody, verifying image integrity, and adhering to industry standards (Source 1). Proper imaging lays the foundation for accurately recovering and analyzing the data.
Analyzing the Image
Once the image has been created, the next step is to analyze it to recover files and artifacts. This involves mounting the forensic image as a virtual drive on the examiner’s computer using forensic software like EnCase or FTK. Mounting provides access to the image like a physical drive without altering the original evidence.
The examiner will then scan the mounted image to extract all available files and artifacts. This may include deleted files, internet history, registry hives, application data, and more. The software uses file carving techniques to reconstruct deleted and fragmented files from unallocated space. Hash libraries help identify known files. Everything extracted is catalogued and can be filtered by type, date, etc. Source
Once extracted, the data will be further analyzed to determine authorship, timeline of activity, program execution, and other details. The examiner looks for incriminating or exonerating evidence relevant to the investigation. Extracted files can also be analyzed through metadata, hex editing, and other means. The analysis aims to tell the story behind the data. Source
Recovering Deleted Files
Recovering deleted files is a major part of forensic data recovery. When a file is deleted from a storage device, the reference to that file’s location on the disk is removed from the file system, but the actual file contents often still exist until being overwritten by new data. Forensic experts use a variety of techniques to locate and reconstruct deleted files from storage media.
One of the main techniques for recovering deleted files is known as file carving. This process searches the raw data on a disk for file signatures and patterns that indicate the start and end of a file. The data between these boundaries can then be extracted as an individual file. File carvers rely on file headers like JPEG and database formats to identify common file types. Custom carving can also locate proprietary or uncommon file formats.
In addition to file carving, experts may attempt to reconstruct corrupted or partially overwritten file systems to regain access to directories and file listings. This allows recovering the filenames, metadata, and directory structure along with the file contents. Rebuilding the file system provides important contextual information that is lost when simply carving file fragments.
Performing data recovery on specialized storage systems like RAID arrays requires an understanding of how the file system stripes and mirrors data across multiple disks. The layout of the RAID configuration must be analyzed to correctly reconstruct the constituent files and volumes.
Challenges arise when trying to recover files from solid state drives (SSDs) where the flash memory cells get reset when deleted. Advanced recovery techniques like scanning for remnant voltage levels can sometimes recover data, but SSDs pose unique difficulties compared to traditional hard drives. Overall, recovering deleted files involves piecing together both high-level file system data as well as low-level information from the raw storage media.
Source: https://www.infotectraining.com/cybersecurity
Bypassing Passwords
One of the key challenges in forensic data recovery is bypassing passwords and encryption that may be protecting files and devices. Investigators have several tools at their disposal to crack or bypass passwords.
Password cracking techniques like brute force, dictionary attacks, and rainbow tables can be used to crack encrypted passwords by trying millions of combinations. Tools like AXIOM Wordlist Generator and hashcat automate this process. However, very complex passwords may still take a long time to crack this way (Magnet Forensics).
In some cases, investigators can bypass the password entirely by gaining physical access to the device and using exploits. For example, on an iPhone they could remove the flash memory chip and access data directly, or install a modchip to bypass encryption. These methods are invasive but can quickly get around even extremely strong passwords (Study.com).
Investigators must also consider legal restrictions, such as laws against unauthorized password cracking, when determining what access methods to use. Overall, bypassing passwords remains a key challenge in investigations involving encryption.
Recovering Damaged Drives
Recovering data from a physically damaged hard drive or storage device often requires specialized tools and expertise. Forensic experts may utilize specialized hardware like a PC-3000 Portable Systems to repair drives with failed controller boards, rebuild RAID arrays, and access data on damaged platters. The drive must be repaired enough to allow data extraction before any file recovery can begin.
For drives with minimal physical damage, data recovery software like PC-3000 UDMA can repair the drive firmware and electronics to regain access to the data. But if platters are damaged or drive heads are broken, a clean room is required for a specialist to transplant working components from a donor drive and attempt raw data recovery. This process is complex, time-consuming, and has no guarantee of success. But for critical drives, rebuilding them in a cleanroom may be the only hope for recovering lost files.
Validating the Recovery
A crucial step in the forensic data recovery process is validating that the files recovered are intact and unaltered. This is done through several methods:
Checking file hashes – The unique hash value of the original file can be compared to the hash value of the recovered file to verify they match exactly. Any change to the file will produce a different hash value. This ensures the integrity of the recovered data. https://www.flashbackdata.com/computer-forensics/forensic-testing/
Verifying recovered data – The recovered files can be opened and viewed to confirm they contain the expected data and were not corrupted in the recovery process. The metadata of files like date created/modified can also be checked.
Maintaining chain of custody – There should be detailed documentation of each step taken during the recovery, who handled the evidence, and the security procedures followed. This ensures the process can be replicated and prevents claims of data tampering.
These validation techniques help ensure the admissibility and reliability of recovered digital evidence in legal proceedings. Proper verification demonstrates the recovery process was forensically sound.
Reporting and Documentation
A critical part of the forensic data recovery process is properly documenting and reporting on the findings. The investigator must create a thorough report that details every step of the recovery, including the tools and techniques used, files and data recovered, and any challenges encountered. Maintaining meticulous notes and logs is crucial for creating an accurate reconstruction of the process.
The forensic report will communicate the key details about the recovered data and serve as evidence in legal proceedings. It should describe the storage device, imaging process, file analysis, and highlight relevant discoveries. The report may point out attempts to delete or conceal data as well as recovered passwords, encryption keys, or hidden partitions. It will also include file listings, registry extracts, and other technical elements.http://cybersecgroup.info/incident-response/computer-forensics/data-recovery-and-forensic-analysis
Thorough documentation removes ambiguity and demonstrates the reliability of the forensic process. Investigators must keep an audit trail showing chain of custody and precise chronological notes. The final report validates the recovery process and serves as a record for all parties involved in a case.
Challenges and Limitations
There are a number of challenges and limitations that forensic data recovery specialists face, including:
Encrypted Devices
Many devices today utilize encryption which can make recovering data extremely difficult or impossible without the proper passwords or keys. Specialists need to stay up-to-date on encryption methods and utilize decryption tools when available.
Damaged Drives
Drives that are physically damaged often require specialized tools and environments like clean rooms to attempt recovery. The range of possible damage introduces uncertainties in the recovery process.
Anti-Forensics
Criminals sometimes utilize anti-forensic techniques like data wiping to cover their tracks. Specialists need countermeasures to deal with these attempts to destroy data.
Staying Current
As technology evolves, new data recovery challenges arise. Specialists must continuously update their tools, techniques, and knowledge to adapt to new devices, operating systems, and data formats.
Overall, while incredible amounts of data can be recovered through forensic techniques, there are always limitations based on the specific circumstances of a case. No method promises perfect data recovery in all situations.
