RomeoWhiskey One

Hunt Hypothesis

This detection identifies the execution of the specific “RomeoWhiskey One” binary pattern across endpoints, signaling potential early-stage adversary activity or legitimate software deployment that requires behavioral validation. Proactive hunting for this signature in Azure Sentinel is essential to establish a baseline of normal operations and distinguish benign processes from subtle, low-severity indicators of compromise before they escalate into significant incidents.

YARA Rule

rule RomeoWhiskey_One
{
	meta:
		copyright = "2015 Novetta Solutions"
		author = "Novetta Threat Research & Interdiction Group - [email protected]"
		Source = "5d21e865d57e9798ac7c14a6ad09c4034d103f3ea993295dcdf8a208ea825ad7"

	strings:
	/*
		FF 15 D8 5B 00 10  call    GetTickCount_9
		0F B7 C0           movzx   eax, ax
		8B C8              mov     ecx, eax
		// skipped: 6A 01              push    1               ; fDecode
		C1 E9 34           shr     ecx, 34h         <--- this value could change
		81 F1 C0 F3 00 00  xor     ecx, 0F3C0h			<--- this value could change
		// skipped: 6A 04              push    4               ; dwLength
		C1 E0 10           shl     eax, 10h
		0B C8              or      ecx, eax
	*/

	$a = {	FF 15 [4]  0F B7 C0 8B C8 [2-4] C1 E9 ?? 81 F1 [2] 00 00 [0-2] 	C1 E0 10 0B C8 	}

	condition:
		$a in ((pe.sections[pe.section_index(".text")].raw_data_offset)..(pe.sections[pe.section_index(".text")].raw_data_offset + pe.sections[pe.section_index(".text")].raw_data_size))
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the RomeoWhiskey One detection rule in an enterprise environment, along with recommended filters or exclusions:

• Scenario: Enterprise Endpoint Protection Scans

  • Context: The YARA rule likely flags file integrity changes or process execution patterns associated with security software. Legitimate daily scans by tools like CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne often trigger these signatures when they update virus definitions, scan critical system directories (e.g., C:\Windows\System32), or perform real-time monitoring of user activities.
  • Suggested Filter: Exclude alerts where the parent process is a known security service (e.g., MsMpEng.exe, csfalcon.exe) and the file path resides within standard antivirus installation directories (%ProgramFiles%\Windows Defender\ or %ProgramData%\CrowdStrike\).

• Scenario: Scheduled Software Patching and Updates

  • Context: Automated patch management tools such as Microsoft SCCM (Configuration Manager), Ivanti, or WSUS frequently execute scripts to download, stage, and install updates during maintenance windows. These processes often create temporary files, modify registry keys, and launch installer executables that match the behavioral logic of the RomeoWhiskey rule, particularly when deploying critical security patches to a large fleet of workstations.
  • Suggested Filter: Create an exclusion for events occurring between 02:00 and 04:00 UTC (maintenance window) where the initiating process is ccmexec.exe or IvAntiVirusAgent.exe, and the target file extension matches known installer types (.msi, .exe) with a “Trusted” publisher signature.

• Scenario: IT Administration via Remote Management Tools

  • Context: System administrators