WAL Frames and SHM Index: Tracking Changes in SQLite
Cadres WAL et index SHM
This specialized micro-course unlocks the forensic potential of Write-Ahead Log (WAL) et Shared Memory (SHM) files—SQLite’s change tracking system that preserves a detailed history of database modifications. While the main database shows you what currently exists, the WAL file reveals what happened before, often containing the smoking gun evidence that suspects thought they had deleted.
Unlike traditional database analysis that only examines static data, WAL forensics gives you a time machine for investigating databases. Every change—from deleted messages and modified contacts to overwritten data—leaves traces in these files that can be recovered and analyzed with the right techniques.
- Deleted data often remains in WAL frames until the next checkpoint operation—potentially preserving crucial evidence
- Each frame represents a specific point in time, allowing reconstruction of database change timelines
- Previous versions of data remain in WAL frames even after being modified or deleted in later committed transactions
- The SHM index provides a roadmap to navigate WAL contents efficiently, even in large files
- Suspect deletes incriminating messages, but they’re preserved in WAL frames
- Modified contact information reveals previous versions with different names or numbers
- Incomplete chat deletions show what the suspect was trying to hide
- Transaction timestamps provide precise timing for evidence tampering attempts
This isn’t theoretical knowledge—you’ll work with real WAL and SHM files, use actual forensic tools, and learn to extract evidence that automated tools might miss. Through practical exercises and visual walkthroughs, you’ll master the techniques needed to recover critical evidence from these often-overlooked files.
Decode the 32-byte WAL header and understand how frames store database page changes over time
Use the Shared Memory file as a roadmap to locate specific frames and track page versions
Extract and interpret individual WAL frames to recover deleted data and track modifications
Build chronological sequences of database changes to understand suspect behavior patterns
Locate and extract deleted messages, contacts, and other critical data from uncommitted transactions
Apply WAL analysis to real-world cases involving data tampering, evidence destruction, and timeline disputes
