E2CbyDoP

Hunt Hypothesis

This detection identifies potential file-based threats by leveraging a specific YARA signature to identify known malicious patterns within the environment. A proactive hunt is essential in Azure Sentinel to uncover dormant or evasive indicators that may not trigger high-severity alerts but could signal early-stage adversary activity requiring further investigation.

YARA Rule

rule E2CbyDoP
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BE [2] BF [2] B9 [2] FC 57 F3 A5 C3 }

condition:
		$a0 at pe.entry_point
}

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 5 specific false positive scenarios for the E2CbyDoP detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Microsoft Defender Antivirus Real-Time Protection Scanning

  • Context: The YARA rule may flag MsMpEng.exe (Microsoft Defender) when it scans executable files in the %TEMP% or user download directories, triggering a match on embedded signatures that resemble the E2CbyDoP pattern.
  • Filter/Exclusion: Exclude processes where ImageName is MsMpEng.exe and the parent process is svchost.exe. Additionally, add an exclusion path for C:\Windows\TEMP to reduce noise from transient file scans.

• Scenario: Scheduled Office 365 ProPlus Updates

  • Context: During business hours, the Microsoft Office Click-to-Run service (OfficeClickToRun.exe) often extracts and installs update packages that contain embedded scripts or manifests matching the E2CbyDoP logic. This is common on workstations running a daily maintenance window.
  • Filter/Exclusion: Create an exclusion for ImageName equal to OfficeClickToRun.exe where the command line contains /update. Alternatively, suppress alerts originating from the C:\Program Files\Microsoft Office directory during defined maintenance windows (e.g., 02:00–04:00).

• Scenario: Endpoint DLP Agent File Indexing

  • Context: Data Loss Prevention (DLP) agents, such as Symantec or Forcepoint, perform background indexing of user documents. The agent process (SymantecDlpAgent.exe or ForcepointEndpoint.exe) often spawns child processes that load policy definitions containing the specific byte patterns detected by E2CbyDoP.