Simplified YARA Rule Tester
Test a small set of required strings against sample content and see whether your rule matches.
YARA is how malware analysts describe what a family looks like so that a machine can find it again. A rule is a set of strings plus a condition, and writing good ones is a balance: too specific and a recompile evades you, too loose and you drown in false positives.
How to use it
- Enter rule strings, one per line — all must match, using simplified "and" logic.
- Paste sample content to test against.
- Adjust until the rule matches what you want and nothing else.
What to take away
Pick strings the author cannot casually change
A hardcoded mutex name, an unusual error string or a distinctive constant survives recompilation. The output filename does not.
Always test against clean files
A rule that matches every sample is worthless if it also matches Notepad. False positives are what get a rule disabled in production.
Real YARA is richer than this
Full YARA supports hex patterns with wildcards, regular expressions, file offsets, module imports and complex boolean conditions. This page teaches the core idea.
Frequently asked questions
What is YARA used for?
Classifying and identifying malware by pattern — in incident response, threat hunting, sandbox pipelines and endpoint tooling. It answers "have we seen this family before, anywhere?"
What makes a rule good?
It matches the whole family including future variants, matches nothing benign, and carries metadata saying who wrote it and why. The third part is what makes it maintainable.
Where do I practise on real samples?
The YARA Rule Builder Challenge gives you three malware samples and one clean file, and asks for a rule that separates them.
Where this fits in the course
This security tool pairs with Path 17 — Malware & RE — see all 26 learning paths.
It runs entirely in your browser: nothing is uploaded, no account is needed, and it is free.
Related
- YARA Rule Builder Challenge — Three malware samples, one clean file. Write a YARA rule that matches every sample and nothing else.
- Malware Strings Triage Lab — A raw strings dump from a suspicious binary. Spot the IOCs — a C2 domain, a mutex, a registry key — before touching a disassembler.
- Regex Tester — Test a regular expression against sample text with live match highlighting and capture groups.
- MITRE ATT&CK Mapper — A searchable reference of real ATT&CK tactics and techniques, tied back to where this course covers each one.