How to Detect and Investigate Anomalous PowerShell Activity Related to Credential Dumping

Credential dumping involves extracting stored passwords or hashes from compromised systems, often targeting sensitive processes like LSASS. Detecting such activity requires careful monitoring of PowerShell usage and correlating logs with security alerts.

---

1. Monitor for PowerShell Scripts Accessing LSASS

What to Look For:

• Script Block Logging:

  • Event ID 4104: Captures executed PowerShell script blocks.

  • Focus on scripts attempting to access LSASS.exe (Local Security Authority Subsystem Service), as it’s a common target for credential dumping tools.

• Indicators:

  • Scripts with direct references to LSASS or tools like Invoke-Mimikatz.

Red Flags: PowerShell scripts attempting to interact with processes like LSASS or referencing credential-related memory areas.

---

2. Check for Use of Suspicious Cmdlets

What to Look For:

• Commonly Abused Cmdlets:

  • Cmdlets often associated with reconnaissance or credential dumping include:

    • Get-Process

    • Get-Service

    • Get-WmiObject

  • These may appear alongside malicious scripts such as Invoke-Mimikatz.

• Behavioral Patterns:

  • Multiple cmdlets used together to identify high-value targets like processes holding credentials.

Red Flags: Cmdlets executed in unusual sequences or contexts, especially by non-administrative accounts.

---

3. Look for Base64 Encoded Commands

What to Look For:

• Encoded Commands:

  • PowerShell commands using the -EncodedCommand parameter are often obfuscated to evade detection.

• Decoding Activity:

  • Decode Base64 strings to reveal their true intent, which might include references to dumping credentials.

Tools: Use decoding utilities or PowerShell itself to analyze the content of Base64-encoded strings.

Red Flags: Encoded commands that decode to scripts targeting credential stores or executing Mimikatz-like functionality.

---

4. Examine PowerShell Command Arguments

What to Look For:

• Process Creation Logs:

  • Event ID 4688: Logs process creation. Focus on:

    • PowerShell commands with arguments such as:

      • -DumpCreds

      • -All

      • Paths to external or suspicious scripts.

• Indicators:

  • Scripts interacting with sensitive directories or services associated with credential storage.

Red Flags: Command arguments indicating dumping or exporting credentials.

---

5. Cross-Reference with Event Logs from Security Tools

What to Do:

• Integrate with Security Solutions:

  • Correlate PowerShell activity with:

    • Alerts from Endpoint Detection and Response (EDR) tools.

    • Anti-malware or intrusion detection systems.

• Behavioral Patterns:

  • Tools blocking or flagging credential dumping attempts often align with suspicious PowerShell commands.

Red Flags: PowerShell activity flagged as potentially malicious by security tools.

---

6. Immediate Response

What to Do:

• Isolate the Affected System:

  • Disconnect the compromised host to contain the threat.

• Reset Compromised Credentials:

  • Immediately reset passwords for all accounts potentially affected.

• Conduct Forensic Analysis:

  • Analyze logs, memory dumps, and other artifacts to determine the method and scope of the breach.

• Strengthen PowerShell Security:

  • Implement stricter PowerShell policies, such as:

    • Enforcing Constrained Language Mode for non-administrative accounts.

    • Restricting PowerShell execution to signed scripts only.

Post-Incident Actions:

• Deploy Enhanced Monitoring:

  • Set up SIEM rules to detect:

    • Obfuscated or encoded commands.

    • Cmdlets associated with credential dumping.

  • Enable real-time alerts for similar patterns.

• Educate Administrators:

  • Train IT teams on secure PowerShell practices and detecting anomalous activity.

• Implement Advanced Security Measures:

  • Use tools like Microsoft Credential Guard to protect LSASS from unauthorized access.

---

Conclusion

Detecting anomalous PowerShell activity related to credential dumping requires monitoring for specific indicators such as interactions with LSASS, suspicious cmdlets, and encoded commands. Proactive analysis and swift response minimize the risk of compromised credentials and further breaches.