RomeoHotel

Hunt Hypothesis

This hypothesis posits that adversaries are deploying the RomeoHotel malware to establish persistent footholds within Azure workloads by leveraging specific code signatures identified through YARA scanning. The SOC team should proactively hunt for this activity in Azure Sentinel to validate low-severity alerts and prevent potential lateral movement before it escalates into a more critical incident.

YARA Rule

rule RomeoHotel
{
	meta:
		copyright = "2015 Novetta Solutions"
		author = "Novetta Threat Research & Interdiction Group - [email protected]"
		Source_64 = "440cb3f6dd07e2f9e3d3614fd23d3863ecfc08b463b0b327eedf08504f838c90"
		Source_diskSpace = "1b1496f8f35d32a93c7f16ebff6e9b560a158cc6fce061491f91bc9f43ef5be4"

	strings:
	/*
		E8 D3 C7 00 00  call    rand
		44 8B ED        mov     r13d, ebp
		44 8B E0        mov     r12d, eax
		B8 1F 85 EB 51  mov     eax, 51EB851Fh
		48 8B FD        mov     rdi, rbp
		41 F7 EC        imul    r12d
		C1 FA 05        sar     edx, 5
		8B CA           mov     ecx, edx
		C1 E9 1F        shr     ecx, 1Fh
		03 D1           add     edx, ecx
		6B D2 64        imul    edx, 64h
		44 2B E2        sub     r12d, edx
		41 83 C4 3C     add     r12d, 3Ch
	*/

	$randBuff64 = {E8 [4] 44 [2] 44 [2] B? 1F 85 EB 51 48 [2] 41 [2] C1 ?? 05 8B ?? C1 ?? 1F 03 ??	6B ?? 64 44 [2]	41 [2] 3C}
		
	/*
		FF 15 40 70 01 10     call    ds:GetDiskFreeSpaceExA
		85 C0                 test    eax, eax
		74 34                 jz      short loc_10005072
		8B 84 24 20 01 00 00  mov     eax, [esp+11Ch+arg_0]
		6A 00                 push    0
		99                    cdq
		68 00 00 10 00        push    100000h
		52                    push    edx
		50                    push    eax
		E8 4C 7C 00 00        call    __allmul
	*/

	$diskSpace = {FF 15 [4] 85 C0 74 ?? 8B [6] 6A 00 99 68 00 00 10 00 5? 5? E8}
		
	$winst = "winsta0\\default" wide		// this limits the overlap with RomeoGolf

	condition:
		$randBuff64 in ((pe.sections[pe.section_index(".text")].raw_data_offset)..(pe.sections[pe.section_index(".text")].raw_data_offset + pe.sections[pe.section_index(".text")].raw_data_size))
		or ($diskSpace 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))
		and $winst)
}

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 3 string patterns in its detection logic.

• Source Rule

False Positive Guidance

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

• Endpoint Protection Scanning of Hotel PMS Archives

  • Scenario: The enterprise’s Endpoint Detection and Response (EDR) agent, such as CrowdStrike Falcon or Microsoft Defender for Endpoint, performs a scheduled deep scan on the “Hotel Property Management System” (PMS) backup directory. This directory contains thousands of legacy .bin files from the RomeoHotel software suite used by the front desk. The YARA rule triggers because these binary archives contain static strings and opcode patterns matching the known signature of the RomeoHotel malware, even though they are legitimate historical data files.
  • Suggested Filter: Create an exclusion for the specific PMS backup path (e.g., \\FileServer\Hotels\RomeoArchive\*) within the EDR console. Additionally, refine the YARA rule to exclude files with a “Last Modified” timestamp older than 90 days if the file hash matches known good baselines of the archive software.

• Automated Deployment via Configuration Management Tools

  • Scenario: During the nightly maintenance window, the IT operations team uses Ansible or Chef to push configuration updates and patch installations for the RomeoHotel booking engine across 50 regional servers. The deployment agent extracts a compressed package containing the RomeoHotel.exe service binary into the system staging folder (C:\Staging\Updates). As the file is written and decompressed, the detection rule triggers on the transient presence of the executable, mistaking the legitimate installation payload for an active threat execution.
  • Suggested Filter: Implement a process-based exclusion that ignores alerts generated by known deployment service accounts (e.g., svc-ansible-deploy or LocalSystem) when the parent