YARA + Sigma + Velociraptor → CrowdStrike Falcon Insight XDR
YARA + Sigma + Velociraptor ↔ CrowdStrike Falcon Insight XDR: integration to migration path.
The OSS stack deploys alongside Falcon Insight first — a Velociraptor canary plus Sigma rules shadow-deployed to Falcon — then takes over authorship, retro hunt and IR collection one phase at a time. No flag day, no re-credentialing, and every step rolls back in minutes.
This is honest co-existence, not a tool fight. Falcon's continuous telemetry, Prevent and OverWatch managed hunting have no OSS parity and stay in place — the OSS layer adds portable content, fleet-wide retro scanning and chain-of-custody evidence that Falcon does not produce.
The idea
Own the content and the IR substrate. Keep Falcon for telemetry and prevention.
The topology that makes this zero-downtime: YARA, Sigma and Velociraptor run as a parallel content and hunt fabric on the same fleet Falcon already covers. Falcon's sensor keeps streaming telemetry and its hunt UI and OverWatch keep running, while Sigma authored once converts to FQL for Falcon (and to KQL and SPL for any SIEM), YARA scans dispatch as Velociraptor artifacts, and Velociraptor handles client-pull IR collection and chain-of- custody packaging Falcon's RTR cannot produce. Content and IR substrate move onto OSS in sequence, each reversible — and Falcon's prevention and managed hunting are never on the table.
The phases
Seven steps. Each one reversible.
Baseline & inventory
We export every Falcon Custom IOA and Custom Detection, map each to ATT&CK, document retention per host tier and 90 days of OverWatch escalation history, and collect every ad-hoc YARA rule before it is lost in analyst home directories. Read-only.
Stand up the content + hunt substrate
A Git repo holds Sigma, YARA and Velociraptor artifacts with CI compiling and testing each. Velociraptor server runs HA and agents deploy to a canary cohort of at most 5% of the fleet, alongside Falcon. No production content yet.
Sigma authorship; dual-deploy to Falcon
A first wave of up to 25 Sigma rules deploys in shadow mode to Falcon Insight via the Custom Detections API while the same rules fire Velociraptor hunts on the canary for ground-truth comparison — catching field-name and event-type drift in the lossy Sigma-to-FQL conversion.
Promote rules; expand fleet coverage
Velociraptor reaches 100% of the fleet in waves, shadow rules are promoted to production in Falcon Insight on a 7-day shadow then 7-day enable cadence, and YARA scans run routinely on IoC-drop events. Sigma-derived detections are tagged so they are distinguishable from vendor IOAs.
Retro hunt + IR runbook integration
Velociraptor becomes the documented step-one IR collection mechanism for any hands-on host, and the retro-hunt playbook ties a new IoC to an authored YARA rule, a fleet hunt, and a comparison against Falcon's same-window Event Search. L3 analysts are trained on VQL basics.
Steady state
Co-existence is the permanent target. OSS owns authorship, retro hunt, on-host YARA and IR-grade collection; Falcon Insight owns continuous telemetry, tier-1/tier-2 hunt UI and vendor-curated IOAs; OverWatch and Prevent are retained as-is. A quarterly content review controls drift.
Detection-engineering shift (optional)
Only if you choose it: detection engineers and tier-3 work primarily in an OSS-fed SIEM rather than Falcon Insight's hunt UI, after Streaming Events ingest is verified and a 30-day overlap proves parity. Tier-1 and tier-2 are unchanged.
Feature parity
Where the OSS stack matches Falcon, and where it honestly does not.
| Capability | YARA + Sigma + Velociraptor | CrowdStrike Falcon Insight XDR | Parity |
|---|---|---|---|
| Detection content | Sigma + YARA rules in Git, portable via pySigma backends | Custom IOA / Custom Detection rules (Falcon DSL) | At parity |
| Continuous endpoint telemetry | Velociraptor is pull-based, not stream-based | LightSensor continuous streaming pipeline (sub-minute latency) | SaaS only |
| On-host file + memory YARA scan | Generic.Forensic.Yara.Scan, Windows.Memory.YaraScan | Falcon Forensics Collector (paid SKU); IOAs match streams, not on-disk patterns | OSS only |
| Retroactive hunt | VQL over the Velociraptor artifact store; replay past collections | Event Search fixed retention (7–90 days); OverWatch hunts forward | OSS only |
| IoC matching against telemetry | Sigma→FQL via pySigma-backend-crowdstrike | Native FQL over Event Search / Custom Detections | Partial |
| Enrichment / ML attribution | ATT&CK chain + IoC overlap; no actor-cluster tag | Embedded ML "Adversary" attribution tag | SaaS only |
| Managed hunting | None — staff it yourself | OverWatch managed hunting (human analysts) | SaaS only |
| IR-grade evidence packaging | Velociraptor ZIP with manifest, SHA-256 per file, chain-of-custody | Falcon RTR stdout (no per-file manifest); Forensics Collector separate SKU | OSS only |
| ATT&CK tagging | Sigma tags: + YARA meta.mitre_attack → attack-navigator JSON | Per-tenant ATT&CK heatmap | At parity |
| On-host arbitrary collection | Velociraptor VQL (registry, EVTX, $MFT, USN, prefetch, AmCache) | RTR scripts (no query engine); Forensics separate | OSS only |
| API surface | Velociraptor server API + VQL; Falcon Rules / Streaming Events API | Falcon Detects / IOA Rules / Streaming Events / Audit Trail API | At parity |
| Audit trail | Velociraptor vfs/audit/ datastore | Audit Trail API (/audit/queries/audit-events/v1) | At parity |
| Deployment & HA | Self-host multi-frontend server + shared MinIO/S3 datastore | Vendor-managed cloud SaaS | SaaS only |
| Cost model | Free software + your compute/ops | Per-endpoint licensing; Forensics / Extended Retention / Streaming separate | Partial |
What we're honest about
The caveats most vendors leave out.
Continuous endpoint telemetry stays with Falcon
Falcon's sensor streams hundreds of event types per host per second into its cloud at sub-minute latency. Velociraptor is pull-based by design, so a fleet scan takes minutes to hours, not real time. We do not cut Falcon Insight as part of this plan — the OSS stack does not replace continuous telemetry, and we mark that a non-goal in writing.
OverWatch and ML attribution have no OSS equivalent
OverWatch's human managed hunting and Falcon's model-backed "this is likely WIZARD SPIDER" attribution tag cannot be replicated by Sigma or YARA. We keep OverWatch and Prevent explicitly out of scope, and substitute attribution with an ATT&CK technique chain plus IoC overlap rather than pretend the speed is matched.
Sigma-to-FQL conversion is lossy
Field names and EDR-specific event types do not round-trip cleanly — a Sysmon ProcessAccess rule has no direct Falcon equivalent. Every rule carries a tests/ corpus asserting it matches Falcon's actual event shape, CI fails on conversion drift, and we maintain an unsupported-on-falcon list rather than ship rules that silently miss.
Two consoles is a real operational cost
Running the OSS fabric alongside Falcon means two queues and two on-call paths, with double-detection on the same event needing SOAR dedupe keyed on host, window and ATT&CK ID. The dual stack must pay for itself in retro hunt, chain-of-custody and YARA value — we re-evaluate every 12 months whether that optionality is justified.
Why this beats a flag day
Reversible in minutes; nothing retired until it has soaked.
Every step rolls back fast — disable a rule in Falcon in under 5 minutes, roll back a deployment wave in under an hour, or revert the IR runbook to Falcon-only collection — because Falcon Insight, Prevent and OverWatch run untouched the whole way through. The only scoped retirement (the optional detection-engineering shift) happens team by team, only after at least a 30-day overlap proves parity, and reverses in under an hour per seat. Co- existence, not cutover, is the deliberate end state.
See whether your detection stack co-exists cleanly.
A 30-minute call with a senior detection-engineering and DFIR engineer. We baseline your Falcon coverage, size your fleet for Velociraptor, and tell you honestly which content and IR work the OSS stack should own — and which Falcon capabilities you keep.
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