TangoBravo

Hunt Hypothesis

This detection identifies potential adversary reconnaissance or initial foothold activities characterized by specific binary patterns defined in the TangoBravo YARA signature within Azure Sentinel workloads. Proactive hunting for this low-severity indicator is essential to uncover stealthy early-stage threats that may not yet trigger high-fidelity alerts but could evolve into significant compromises if left uninvestigated.

YARA Rule

rule TangoBravo
{
	meta:
		copyright = "2015 Novetta Solutions"
		author = "Novetta Threat Research & Interdiction Group - trig@novetta.com"
		Source = "2aa9cd3a2db2bd9dbe5ee36d9a5fc42b50beca806f9d644f387d5a680a580896"

	strings:
	/*
		50                 push    eax             ; SubStr
		55                 push    ebp             ; Str
		FF D3              call    ebx ; strstr
		83 C4 08           add     esp, 8
		85 C0              test    eax, eax
		75 1A              jnz     short loc_401131
		8A 8E 08 01 00 00  mov     cl, [esi+108h]
		81 C6 08 01 00 00  add     esi, 108h
		47                 inc     edi
		8B C6              mov     eax, esi
		84 C9              test    cl, cl
		75 E2              jnz     short loc_40110C
	*/

	$targetDomainCheck = {5? 5? FF ?? 83 C4 08 85 C0 75 ?? 8? ?? 08 01 00 00 8? ?? 08 01 00 00 4? 8B ?? 84 ?? 75  }

	condition:
		$targetDomainCheck 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 TangoBravo detection rule in an enterprise environment, along with suggested filters or exclusions:

• Scenario: Automated Endpoint Patch Deployment via SCCM/MECM

  • Context: During scheduled maintenance windows, System Center Configuration Manager (SCCM) agents push critical security patches. The deployment process involves the ccmexec.exe service spawning child processes that download and unpack CAB files containing executable payloads, which may match the TangoBravo signature for “suspicious script execution within a temporary directory.”
  • Filter/Exclusion: Exclude file paths containing C:\Windows\CCM\Logs or process names starting with ccmexec.exe. Additionally, whitelist the specific SHA-256 hashes of known patch installer templates used by the organization’s IT Operations team.

• Scenario: Microsoft Defender for Endpoint (MDATP) Real-Time Scanning

  • Context: The native Windows Defender Antivirus engine performs real-time scanning and heuristic analysis. When a user opens a large Excel workbook with embedded macros, MsMpEng.exe may spawn a temporary worker process to analyze the macro code in memory. This activity often mimics the behavior of a malicious script interpreter triggering the TangoBravo rule.
  • Filter/Exclusion: Create an exclusion for the parent process MsMpEng.exe and its child processes running under the service account NT SERVICE\MsMpSvc. Filter out events where the file path is located within the C:\ProgramData\Microsoft\Windows Defender\Scans\Temp directory.

• Scenario: CI/CD Pipeline Artifact Extraction (Jenkins/GitLab Runner)

  • Context: Build servers running Jenkins or GitLab Runners frequently extract Docker images and application artifacts during nightly builds. The extraction process involves unzipping archives containing thousands of scripts and