Community Sigma and YARA: useful detection sharing without giving up control.

Detection engineering improves when defenders can safely learn from each other. Sigma and YARA are two of the most practical formats for doing that: Sigma captures behavior in logs, while YARA captures file, script, document, and malware-content traits.

The hard part is not deciding whether sharing is valuable. The hard part is making sharing safe enough that customers can participate without exposing internal context, proprietary details, or operational assumptions.

Private by default

Threat Foundry treats customer-generated rules as private by default. A tenant has to opt in under Core configuration before community sharing is active. Even then, custom Sigma and YARA builder workflows keep sharing visible with a small checked control that analysts can clear before saving.

Autogenerated rules should contribute when customers opt in

When a customer enables community participation, autogenerated Sigma and YARA rules can become part of a useful feedback loop. CTI becomes detection logic, analysts review and save it, and the sanitized rule can help other opted-in defenders who are facing similar threats.

Sanitized, review-first content

Shared rules are sanitized before community distribution. The first pass focuses on obvious customer-specific values like private IPs, internal domains, ticket identifiers, and host or tenant assignment lines. That sanitizer is a guardrail, not a replacement for analyst review.

Imported community rules should also remain review-first. The goal is not blind deployment. The goal is to give teams a better starting point: detection logic with context, mapped to the right lane, and ready for local tuning.

Sigma and YARA belong together

Sigma and YARA solve different parts of the detection problem. A strong community exchange should support both. If CTI describes process behavior, authentication patterns, registry activity, DNS, or proxy telemetry, Sigma is usually the right path. If CTI exposes file strings, payload markers, byte patterns, macros, packer traits, or malware family artifacts, YARA is the better fit.

More rules is not the goal. Better reviewed, better contextualized, reusable detection logic is the goal.

This is the direction we are building toward with Threat Foundry: community-assisted detection engineering that is private by default, opt-in by design, and practical for teams that need to turn intelligence into action.