IndiaBravo RomeoCharlie

Hunt Hypothesis

This detection targets adversary behavior involving specific code patterns identified by the IndiaBravo RomeoCharlie YARA signature, which may indicate early-stage reconnaissance or benign tool usage often missed by standard alerts. Proactively hunting for this pattern in Azure Sentinel is critical to validate its context and distinguish between legitimate operational activity and potential low-fidelity threats that could evolve into more significant incidents if left unmonitored.

YARA Rule

rule IndiaBravo_RomeoCharlie
{
	meta:
		copyright = "2015 Novetta Solutions"
		author = "Novetta Threat Research & Interdiction Group - [email protected]"
		Source = "58ad28ac4fb911abb6a20382456c4ad6fe5c8ee5.ex_"
		Status = "Signature is too loose to be useful."
		
	strings:
	/*
		50                 push    eax             ; argp
		68 7E 66 04 80     push    8004667Eh       ; cmd
		8B 8D DC FE FF FF  mov     ecx, [ebp+skt]
		51                 push    ecx             ; s
		FF 15 58 31 41 00  call    ioctlsocket
		83 F8 FF           cmp     eax, 0FFFFFFFFh
		75 08              jnz     short loc_4043F0
	*/

	$a = {50 68 7E 66 04 80 8B 8D [4] 51 FF 15 [4] 83 F8 FF 75}
	$b1 = "xc123465-efff-87cc-37abcdef9"
	$b2 = "[Check] - PORT ERROR..." wide
	$b3 = "%sd.e%sc n%ssh%srewa%s ad%s po%sop%sing T%s %d"

	condition:
		2 of ($b*) or 
		$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 4 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the IndiaBravo RomeoCharlie detection rule, tailored for an enterprise environment using common security and administrative tools:

• Scenario: Automated Patch Deployment via SCCM

  • Context: The System Center Configuration Manager (SCCM) agent executes a scheduled task during the maintenance window to deploy critical OS updates. This process involves the execution of temporary scripts (powershell.exe or msiexec) that download and install binaries, triggering the YARA signature due to specific file manipulation patterns in the %TEMP% directory.
  • Suggested Filter/Exclusion: Create an exclusion for processes initiated by ccmsetup.exe or wuauserv.exe where the parent process is CcmExec.exe, specifically filtering out events originating from the “Software Update” collection group during defined maintenance windows (e.g., 02:00–06:00 UTC).

• Scenario: Endpoint Antivirus Real-Time Scanning

  • Context: The enterprise endpoint protection suite, CrowdStrike Falcon, performs a scheduled deep scan of the C:\ProgramData\Microsoft directory. During this scan, the antivirus engine extracts compressed archives and writes temporary files that match the heuristic logic defined in the IndiaBravo_RomeoCharlie YARA rule, flagging them as suspicious activity despite being benign system operations.
  • Suggested Filter/Exclusion: Exclude events where the process name is Cortex.sys or FalconSensorService.exe and the file path contains \Microsoft\Windows\SoftwareDistribution\. Additionally, add a whitelist for the specific SHA-256 hash of the CrowdStrike sensor binary to prevent self-triggering.

• Scenario: Backup Agent Data Synchronization

  • Context: The Veeam Backup & Replication agent runs an