LIVE NEWSROOM · --:-- · May 15, 2026
A LIBRARY FOR SECURITY RESEARCHERS

TOOLS  /  YARA RULE TESTER

YARA Rule Tester

Paste a YARA rule and a sample (text or upload, max 100KB). We compile the rule (syntax errors caught), match it against the sample, and report hits.

Or (max 100KB).

    What it does

    YARA is the de-facto standard for malware classification rules. Writing rules is straightforward; testing them against real samples without a local install isn’t. Our tester compiles your rule, surfaces syntax errors with line numbers, and runs the match against a sample (text or uploaded file up to 100 KB). Results include matched rule names, tags, and the exact strings that triggered each match. Compute runs on our microservice — your sample data is processed in-memory and not persisted.

    How to use it

    1. Paste a YARA rule in the rule editor. Standard YARA 4.x syntax is supported.
    2. Paste suspicious text in the sample box, or upload a binary file (max 100 KB).
    3. Click "Run YARA test" — compile errors surface immediately; matches return in 1–3 seconds.
    4. Iterate: tweak rule thresholds (e.g. condition string counts) and re-run.
    5. Save working rules to your local repository when satisfied with detection.

    Common use cases

    Detection-rule development Build YARA rules for a new malware family and iterate against known samples before deploying to production scanners.
    Threat hunting Test "broad-spectrum" YARA rules against historical samples to validate hit rate and false-positive ratio.
    Incident response During active response, write quick YARA rules to identify additional infected hosts from a known sample.
    Education Learn YARA syntax by trying example rules from the wild against test files.

    Frequently asked questions

    Why does my rule fail to compile? +
    YARA syntax is strict. Common errors: missing condition keyword, unterminated strings (curly brace counted instead of bracket), regex syntax errors. The error message includes a line number.
    Can I test against large samples? +
    Free tier: 100 KB max sample. For larger samples or batch matching, install YARA locally — official builds at virustotal.github.io/yara/.
    Is my rule stored? +
    No. Rules are processed in-memory by our microservice and discarded after the response is sent. Your detection logic stays private.
    Why "service not deployed yet"? +
    The YARA microservice runs separately from WordPress (Python + yara-python on Fly.io). Once deployed, this disappears and matches return live.
    Difference vs Sigma? +
    YARA = file/sample matching (binary, text content). Sigma = log/event matching (SIEM detection). Use YARA for malware classification, Sigma for log-based detection.

    Related tools

    Related coverage on Ciphers Security

    Free for everyone, no signup required. Tool runs at /tools/yara-tester/ — bookmark or share.

    Scroll to Top