Migration Helper Generate Rule

Generate YARA-L 2.0 Rule (Alias)

Description

Migrates the legacy source rule section inside the <rule_name>.yaral template file to a valid Google SecOps YARA-L 2.0 detection rule.

When to Use This Skill

• Use this skill to translate the original logic of a legacy rule into YARA-L 2.0 syntax.
• Triggered by /migration_helper_generate_rule <rule_name> (where <rule_name> is the name of the rule directory, i.e., rules/<rule_name>/<rule_name>.yaral).

Instructions

Please refer to the main skill migration_helper_generate_yaral for full instructions.

Your primary role is to migrate the Source Rule section in rules/<rule_name>/<rule_name>.yaral into YARA-L 2.0. Be sure to present your plan and await approval.

Steps:

1. Rule File Reading: Read the file rules/<rule_name>/<rule_name>.yaral. If lines are shortened or you receive a truncation error, immediately stop.
2. Detailed Analysis: Perform a detailed analysis of the rule under the SOURCE RULE block.
3. Context-Aware Reference Searching: Search for the most similar existing YARA-L rules (excluding the current file) in your repository that contain similar description keywords, and use them as context for logic creation.
   • Example: For input rules with description "Rare or Never Seen EventID Logged", search for rules with "first time seen window event" or "rare or never seen EventID".
4. Logic Planning: Plan for an exact like-for-like migration to YARA-L 2.0. Refer to YARA-L 2.0 syntax conventions and examples. You are forbidden from simplifying rule logic or taking shortcuts.
5. Placement: Place the migrated YARA-L 2.0 rule content between the first and last line at <YARA-L 2.0 rule content> in the existing file rules/<rule_name>/<rule_name>.yaral.

Meta Schema Requirements:

Ensure the meta block of the migrated YARA-L 2.0 rule follows this exact schema:

• author = must be "Google Professional Services"
• description = must be the exact like-for-like description as the source rule.
• title = must be the exact like-for-like title as the source rule.
• tactic = must be "TO-BE-FIXED"
• technique = must be "TO-BE-FIXED"
• mitre_attack_url = must be "https://attack.mitre.org/techniques"
• mitre_attack_version = must be "TO-BE-FIXED"
• old_ucid = must be "TO-BE-FIXED"
• secops_ucid = must be "TO-BE-FIXED"
• type = must be "Alert"
• data_source = must be "TO-BE-FIXED"
• responsible = must be "SOC1"
• creation_date = Must contain exact like-for-like creation as the source rule in DD.MM.YYYY format (Example: "16.06.2025"). Can be empty ("") if not found.
• last_rework_date = Today's date in DD.MM.YYYY format (Example: "16.06.2025"). Can be empty ("").
• severity = must be exact like-for-like severity as the source rule ("Medium", "High", "Low"). If not set, use "TO-BE-FIXED".
• status = must be "prototype"
• version = must be "0.5"