Question

A detection engineer maintains a YARA-L single-event rule that flags PowerShell execution with the '-nop -w hidden' flags. The rule generates frequent false positives from three sanctioned internal automation hosts, and the security team expects that list of approved hosts to grow and change over the coming months as new automation servers are provisioned. The engineer wants to suppress these known-good hosts while keeping the tuning maintainable and auditable, without redeploying the rule each time the host list changes. Which approach best meets these requirements?

Accepted Answer

Reference a managed reference list of approved automation hostnames in the rule's condition (e.g., not principal.hostname in %approved_automation_hosts%), and update the list independently of the rule.

Answer

Add an inline condition to the rule excluding each host by name (e.g., not principal.hostname = "auto01" and not principal.hostname = "auto02"), editing the rule whenever the list changes.

Answer

Lower the rule's severity to Informational so the false positives no longer generate alerts, leaving the detection logic unchanged.

Answer

Disable the rule during automation maintenance windows and re-enable it afterward using a scheduled rule state change.