Toward next-generation DFIR triage: E01 imaging of selectively collected artifacts

Abstract

DFIR field triage after a breach needs fast collection and evidence that opens immediately in standard forensic tools. Full-disk imaging provides compatibility and chain of custody, but is slow and large. Selective acquisition tools such as KAPE, CyLR, and Velociraptor are faster, but their output is split into file copies and sidecar metadata files.

We propose a single-pass processing flow that writes NTFS regions selected by policy directly to an EWF1/E01 evidence container. Selected regions are stored as compressed chunks, while unselected regions are represented as logical zero regions. The output therefore keeps the source volume’s logical size and NTFS layout. FTK Imager, Magnet AXIOM, and X-Ways recognized this E01 without separate conversion.

On a NIST CFReDS 20.00 GB NTFS image under a 23-rule triage policy, the reference implementation generated a 308 MB E01 with a 42.28 s median over 5 runs, and the repeated outputs were byte-identical. A single run on a 446.02 GB incident-response partition generated a 1.09 GB E01. In the CFReDS comparison with KAPE, the proposed method took longer, but produced a single E01 container with container-level metadata and integrity verification.

The results depend on the selection ratio and data compressibility. If the policy selects many already compressed video or archive files, the output ratio and throughput bottleneck may change. The E01 container hash is computed over a logical disk made of selected regions and zero regions, so file identity in selective seizure must be interpreted together with a separate per-file hash manifest.