Hunting for Credential Dumping Abuse

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Hunting for Credential Dumping Abuse: A Realistic Threat Hunting Investigation

Why This Activity Stood Out

During our routine monitoring, we noticed some peculiar events that piqued our interest. Specifically, rundll32.exe was being used in a way that didn’t quite fit the typical user behavior. It seemed out of place and warranted further investigation.

Initial Hunt Logic

Our initial hunch was that this activity might be related to credential dumping. Adversaries often use tools like rundll32.exe to execute malicious pay-loads or access sensitive information stored in LSASS (Local Security Authority Subsystem Service). This led us to scrutinize the process lineage and command-line arguments.

Reviewing Process Lineage

To better understand what was going on, we started by tracing back from rundll32.exe. Using Process Explorer, we followed its parent processes and any child processes it spawned. The trail revealed a complex chain of activities that didn’t look right:

  1. Initial Process: A seemingly normal user login with an interactive session.
  2. Parent Process: An elevated PowerShell script executed as part of routine maintenance.
  3. Child Process: rundll32.exe with suspicious command-line arguments.

Expanding the Investigation

Given the complexity, we broadened our investigation to cover additional telemetry sources:

  • Sysmon Event ID 10: This provided detailed process creation events and network activity.
  • Security Logs: For broader context on user actions.
  • EDR Telemetry: To gather endpoint detection data.

Detection Opportunities

We used a Sigma rule for suspicious encoded PowerShell to spot potential malicious activities:

title: Suspicious Encoded PowerShell

logsource:
  category: process_creation

detection:
  selection:
    CommandLine|contains:
      - '-enc'
      - 'EncodedCommand'

condition: selection

level: high

And ran KQL and SPL queries to further analyze suspicious rundll32.exe activities:

DeviceProcessEvents
| where FileName =~ "rundll32.exe"
| project Timestamp, DeviceName, InitiatingProcessCommandLine

index=sysmon Image="*rundll32.exe" 
| stats count by Computer, CommandLine

Analyst Notes

  1. Initial Uncertainty: Initially, the activity seemed legit as it involved a user and some administrative tasks.
  2. Suspicious CommandLine Arguments: The use of '-enc' in command-line arguments was a red flag.
  3. Network Activity: No immediate network connections from rundll32.exe, but this could be an evasion tactic.

Operational Challenges

  1. False Positives: Benign software can sometimes trigger false positives, especially when using common tools like PowerShell and rundll32.exe.
  2. Telemetry Blind Spots: Some processes might not emit enough telemetry to catch suspicious activities if they are well-hidden.
  3. Complexity of Process Lineage: Tracing back the process lineage required patience and detailed scrutiny.

MITRE ATT&CK Mapping

This investigation aligns with the following MITRE ATT&CK techniques:

  • T1003 – Credential Dumping:
    • Description: Adversaries may attempt to access LSASS memory or credential stores to obtain account credentials.
    • Techniques: Using rundll32.exe and suspicious command-line arguments.

Practical Detection Recommendations

Telemetry Improvement Ideas

  1. Enhanced Sysmon Configurations:

    • Add more detailed event logging for process creation, network activity, and file operations.

  2. Behavioral Analytics:

    • Implement behavioral analytics to detect anomalies in process behavior and command-line arguments.

  3. Endpoint Detection Tools:

    • Ensure all EDR tools are configured to capture detailed information about process execution and network communications.

Realistic Hunting Methodology

  1. Detailed Telemetry Analysis:

    • Regularly review Sysmon logs, Security Logs, and EDR telemetry for suspicious activities.

  2. Process Lineage Tracing:

    • Use Process Explorer to trace the lineage of suspicious processes back to their origins.

  3. Threat Actor Indicators:

    • Continuously monitor for known threat actor IoCs such as rare domains or specific command-line arguments.

Hashtags

ThreatHunting #CredentialDumping #WizardSpider #T1003 #MITREATT&CK #ProcessLineage #SysmonTelemetry #EDRAnalytics

This article provides a realistic view of a threat hunting investigation for credential dumping abuse, detailing the process from initial hypothesis to detailed analysis and detection. It reflects the practical challenges and insights gained during such investigations in a real-world SOC environment.

#ThreatHunting #CyberSecurity #BlueTeam #SOC #DetectionEngineering #MITREATTACK #CredentialAccess #Windows #CredentialDumping