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yara-rule-authoring

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Use when writing, reviewing, optimizing, validating, or migrating YARA or YARA-X malware-detection rules, including CRX or DEX rules. Not for network IDS or memory-forensics rules.

.devin/skills/yara-rule-authoring/SKILL.md

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# YARA-X rule authoring

## Contract

| Field | Bound contract |
|---|---|
| Trigger | The user asks to write, review, tighten, optimize, validate, or migrate YARA or YARA-X malware-detection rules, including CRX or DEX module rules. |
| Authority | Reversible local: writes only YARA-X rule files on disk; rollback is file deletion or VCS revert. No remote mutation. Runs yr, yara_lint.py, atom_analyzer.py, sample scans, and goodware scans; no credential access, publishing, or deployment. |
| Side effect | May create or modify YARA-X rule files and run yr, yara_lint.py, atom_analyzer.py, sample scans, and goodware scans. Tool output must distinguish syntax/style/atom defects, positive matches, negative-corpus matches, timing, and unperformed validation rather than collapsing them into one verdict. |
| Done | The resulting rule has family-specific indicators and cheap prefilters, correct endianness and module use, required metadata, bounded performant patterns, passing yr check/format/linter results, documented positive-sample coverage, and zero measured goodware matches, or explicitly states which validation was not run and why. |

## Inputs

- Rule source or specification (required): existing rule to review/optimize/migrate, samples to write against, or IOC/threat-intel to convert.