Tools / Google SecOps Interview questions
Explain the difference between the meta, events, and condition sections of a YARA-L rule?
These three required sections each play a distinct role in a YARA-L rule, moving from documentation, to pattern definition, to the actual triggering logic.
rule failed_login_spike { meta: author = "detection-team" severity = "High" description = "Detects a burst of failed logins for one user" events: $fail.metadata.event_type = "USER_LOGIN" $fail.security_result.action = "BLOCK" $fail.target.user.userid = $user condition: #fail > 5 }
The meta section carries descriptive metadata — author, severity, description — that documents the rule for other analysts without affecting its detection logic at all; it's required specifically so shared detection rules remain understandable and attributable over time, especially as a rule set grows and is maintained by more than one person.
The events section defines the pattern of UDM fields a matching event (or events, in a multi-event rule) must satisfy, using event variables (like $fail above) to reference and constrain specific fields; the condition section then specifies the logical test over those defined events — in this example, whether the count of matching failed-login events (#fail) exceeds five — that actually determines whether the rule fires a detection.
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