Glossary
Atom
An atom is the short fixed byte sequence YARA extracts from each pattern and searches for first; atom quality drives scan speed.
Before scanning, YARA chooses for every pattern a fixed substring of up to four bytes, the atom. All atoms are searched simultaneously with an Aho-Corasick automaton; the full pattern is verified only where its atom appears. Rare atoms mean few verifications and fast scans; common atoms such as 00 00 or a three-letter string trigger verifications everywhere.
The performance guide and the linter help you choose patterns with good atoms.