In many incident response scenarios, shutting down a machine is not an option as it would destroy critical volatile evidence. This is where you need to know how to perform a live forensic disk image acquisition. A live acquisition involves creating a bit-for-bit copy of a storage device while the system is still running. Using tools available in Kali Linux, you can capture this data while minimizing changes to the system state and ensuring the integrity of your evidence.
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⚡ Why Live Acquisition is Crucial for Volatile Data
Traditional forensics often involves offline imaging, where a system is powered down. However, this erases all data in volatile memory (RAM), which can contain running processes, network connections, and active malware. While a live *disk* acquisition doesn’t capture RAM, it is the necessary counterpart for investigating a running system where shutdown is impractical. It allows you to capture the disk’s state while preserving the volatile evidence in RAM for a separate memory acquisition, providing a more complete picture of the system at the time of the incident.
💾 How to Use ddrescue for Reliable Disk Imaging
While the standard `dd` command can create a disk image, a much better tool for forensic work is `ddrescue`. Unlike `dd`, which may fail on read errors, `ddrescue` is designed to handle failing drives by intelligently skipping bad sectors and coming back to them later. This is crucial for acquiring data from damaged media. To perform a live acquisition, you would run a command like `sudo ddrescue -f -n /dev/sda /mnt/forensic_storage/image.dd /mnt/forensic_storage/mapfile.log`, where `/dev/sda` is the source disk. This command creates an image, `image.dd`, and a log file that tracks the progress, making the process resumable.
🔐 How to Ensure Evidence Integrity with Hashing
The single most important principle in digital forensics is evidence integrity. You must be able to prove that the acquired image is an exact, unaltered copy of the original source. This is achieved by calculating cryptographic hashes (preferably SHA-256) of the source disk and the final image file. In a live acquisition, the source disk is constantly changing, so it’s best practice to hash the source device immediately at the start of the imaging process and then hash the resulting image file once it’s complete. These two hash values should match. Meticulous logging of every command, timestamp, and hash value is essential for maintaining the chain of custody.
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Johnson, Richard. Kali Linux Essentials. NOBTREX LLC, 2025.
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