OffsetInspect v3.0.0 – track how Defender signature updates shift detection boundaries across a corpus [PowerShell, MIT]

Built this to answer a specific detection-engineering question: when Defender pushes a definition update, does the detection boundary on your known-bad corpus move, disappear, or newly appear on something previously clean?

`Compare-OffsetThreatResult` diffs two scan results for the same file and classifies the change — NewlyDetected, NoLongerDetected, BoundaryEarlier, BoundaryLater, BoundaryUnchanged, BothClean — along with the byte delta. Running that across a corpus with `Invoke-OffsetThreatScanBatch` gives you a detection-shift matrix you can track over time across definition versions.

Boundary results report DetectionPrefixLength (prefix N-1 was clean, prefix N triggered), a confidence rating, and a ProbeLog showing how stable that boundary held across repeated probes. The tool is explicit that this identifies the earliest triggering prefix — not necessarily the complete signature, since AV decisions can depend on tokenization, surrounding context, and provider state. For files with multiple independently-detectable regions, `Invoke-OffsetThreatScanRegion` segments the file and scans each piece through AMSI entirely in memory — nothing written to disk, no real-time protection interference — bisecting each hit to an absolute file offset. Useful for understanding how much of a file's detectable content would survive targeted evasion of just the first boundary.

Scan results export to Markdown/HTML with a full per-invocation ProbeLog audit trail, intended to be attachment-ready for engagement writeups.

Composes with YARA rules (hits return offsets you pipe into context inspection), PE/imphash parsing, per-window Shannon entropy for spotting packed regions before running boundary analysis, and string extraction with byte offsets.

AMSI/Defender providers are Windows-only. Everything else is cross-platform.

GitHub: https://github.com/warpedatom/OffsetInspect

PowerShell Gallery: Install-Module OffsetInspect