Writing YARA Rules

A good YARA rule matches the malware's nature — its code, its structure, its unavoidable constants — not its costume, which is a filename or a mutable string that changes on the next build. Match the nature and the rule survives recompilation and catches the whole family; match the costume and you catch one sample once. The entire craft is choosing strings and a condition that are both specific enough to avoid false positives and durable enough to generalize.

When to Use

• Writing a YARA rule to detect a malware family, tool, or capability
• Creating a signature for a file or in-memory artifact from a known sample
• Turning IOCs or a captured specimen into a portable, testable detection
• Hunting for a family across a corpus (VirusTotal Retrohunt, LOKI/THOR, on-host scan)
• Clustering related samples by shared code, constants, or structure
• Reviewing or tuning an existing rule for false positives and scan performance

When NOT to Use