Detect vSphere Installation Bundles in Splunk
Adversaries abuse VMware vSphere Installation Bundles (VIBs) to achieve persistent access on ESXi hypervisors. VIBs are software packages that persist across reboots by being incorporated into the ESXi boot image. Malicious VIBs can deploy backdoors, custom firewall rules, and startup scripts. UNC3886 used malicious VIBs to install VIRTUALPIE backdoor on ESXi. VIBs can be installed with --force flag to bypass acceptance level requirements, and adversaries masquerade them as PartnerSupported by modifying the XML descriptor. ESXi detection is challenging due to limited logging.
MITRE ATT&CK
- Tactic
- Persistence
- Technique
- T1505 Server Software Component
- Sub-technique
- T1505.006 vSphere Installation Bundles
- Canonical reference
- https://attack.mitre.org/techniques/T1505/006/
SPL Detection Query
index=wineventlog (sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" OR sourcetype="syslog")
| eval detection_type=case(
sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" AND EventCode=1 AND
(match(Image, "(?i)(esxcli|powercli|vmwarecli)\.exe") OR
match(CommandLine, "(?i)(software\s+vib\s+install|--vibs|esxcli\s+software)")),
"VIB_CLI_Install_Command",
sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" AND EventCode=1 AND
match(Image, "(?i)(powershell|pwsh)\.exe") AND
match(CommandLine, "(?i)(Install-EsxSoftwarePackage|Add-EsxSoftwareDepot|esxcli\.software\.vib)"),
"VIB_PowerCLI_Management",
sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" AND EventCode=11 AND
match(TargetFilename, "(?i)\.(vib|vgz)$"),
"VIB_File_Drop",
sourcetype="syslog" AND
match(_raw, "(?i)(software\s+vib\s+install|esxcli.*vib.*install|--force.*vib)"),
"ESXi_VIB_Install_Syslog",
true(), null()
)
| where isnotnull(detection_type)
| table _time, host, User, detection_type, Image, CommandLine, TargetFilename
| sort - _timeDetects vSphere VIB installation activity via Sysmon (for Windows management hosts) and syslog (for direct ESXi shell activity if syslog forwarding is configured). Covers esxcli VIB install commands, PowerCLI VIB management cmdlets, VIB file creation, and ESXi syslog entries for VIB installation commands.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Authorized VIB deployments by VMware admins for patching or driver updates
- VMware Update Manager scheduled patch operations
- vSAN or NSX component VIB deployments
Other platforms for T1505.006
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1List Installed VIBs on ESXi Host
Expected signal: ESXi shell audit log: esxcli command execution. If ESXi syslog is forwarded: syslog entry for esxcli invocation.
- Test 2Check ESXi VIB Acceptance Level
Expected signal: ESXi shell audit log for esxcli execution.
- Test 3Simulate VIB Install CLI Command on Windows Management Host
Expected signal: Sysmon EventCode 1: powershell.exe with CommandLine containing 'vib install' and '--force'.
References (4)
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