Remote WMI Wbemcomn DLL Hijack

Metadata

collaborators

[‘Roberto Rodriguez @Cyb3rWard0g’, ‘Jose Rodriguez @Cyb3rPandaH’]

creation date

2020/10/09

modification date

2020/10/09

playbook related

[‘WIN-201012004336’]

Hypothesis

Threat actors might be copying files remotely to abuse a DLL hijack opportunity found on the WMI provider host (wmiprvse.exe).

Technical Context

Windows Management Instrumentation (WMI) is the Microsoft implementation of Web-Based Enterprise Management (WBEM), which is an industry initiative to develop a standard technology for accessing management information in an enterprise environment. WMI uses the Common Information Model (CIM) industry standard to represent systems, applications, networks, devices, and other managed components. WMI resides in a shared service host with several other services. To avoid stopping all the services when a provider fails, providers are loaded into a separate host process named “Wmiprvse.exe”. More than one process with this name can be running. The shared host can run under one of the following system accounts in a Wmiprvse.exe host process:

  • LocalSystem

  • NetworkService

  • LocalService When wmiprvse.exe handles a network connection, it runs under the NETWORK SERVICE account. A Threat actor could try to run code as a Network Service user leveraging the WMI provider host process.

Offensive Tradecraft

A threat actor could use a known DLL hijack vulnerability on the execution of wmiprvse.exe to accomplish code execution as a NETWORK SERVICE account. One way to perform a DLL hijack on the WMI provider host is via the wbemcomn DLL. When wmiprvse.exe triggers, it looks for wbemcomn.dll in the C:\Windows\System32\wbem\ directory. That DLL does not exist in that folder. Therefore, a threat actor could easily copy its own DLL in that folder and execute it with the WMI provider host. When the malicious DLL is loaded, there are various approaches to hijacking execution, but most likely a threat actor would want the DLL to act as a proxy to the real DLL to minimize the chances of interrupting normal operations. One way to do this is by cloning the export table from one DLL to another one. One known tool that can help with it is Koppeling.

Mordor Test Data

metadata

https://mordordatasets.com/notebooks/small/windows/08_lateral_movement/SDWIN-201009173318.html

link

https://raw.githubusercontent.com/OTRF/mordor/master/datasets/small/windows/lateral_movement/host/covenant_wmi_wbemcomn_dll_hijack.zip

Analytics

Initialize Analytics Engine

from openhunt.mordorutils import *
spark = get_spark()

Download & Process Mordor Dataset

mordor_file = "https://raw.githubusercontent.com/OTRF/mordor/master/datasets/small/windows/lateral_movement/host/covenant_wmi_wbemcomn_dll_hijack.zip"
registerMordorSQLTable(spark, mordor_file, "mordorTable")
[+] Processing a Spark DataFrame..
[+] DataFrame Returned !
[+] Temporary SparkSQL View: mordorTable 

Analytic I

Look for non-system accounts SMB accessing a C:\Windows\System32\wbem\wbemcomn.dll with write (0x2) access mask via an administrative share (i.e C$).

Data source

Event Provider

Relationship

Event

File

Microsoft-Windows-Security-Auditing

User accessed File

5145

df = spark.sql(
'''
SELECT `@timestamp`, Hostname, ShareName, SubjectUserName, SubjectLogonId, IpAddress, IpPort, RelativeTargetName
FROM mordorTable
WHERE LOWER(Channel) = "security"
    AND EventID = 5145
    AND RelativeTargetName LIKE '%wbem\\\wbemcomn.dll'
    AND NOT SubjectUserName LIKE '%$'
    AND AccessMask = '0x2'
'''
)
df.show(10,False)
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|@timestamp             |Hostname                   |ShareName|SubjectUserName|SubjectLogonId|IpAddress  |IpPort|RelativeTargetName                |
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|2020-10-09 17:34:28.926|WORKSTATION6.theshire.local|\\*\C$   |pgustavo       |0x227a012     |172.18.39.5|50963 |Windows\System32\wbem\wbemcomn.dll|
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+

Analytic II

Look for C:\Windows\System32\wbem\wbemcomn.dll being accessed over the network with write (0x2) access mask via an administrative share (i.e C$) and created by the System process on the target system.

Data source

Event Provider

Relationship

Event

File

Microsoft-Windows-Security-Auditing

User accessed File

5145

File

Microsoft-Windows-Sysmon/Operational

Process created File

11

df = spark.sql(
'''
SELECT `@timestamp`, Hostname, ShareName, SubjectUserName, SubjectLogonId, IpAddress, IpPort, RelativeTargetName
FROM mordorTable b
INNER JOIN (
    SELECT LOWER(REVERSE(SPLIT(TargetFilename, '\'))[0]) as TargetFilename
    FROM mordorTable
    WHERE Channel = 'Microsoft-Windows-Sysmon/Operational'
        AND Image = 'System'
        AND EventID = 11
        AND TargetFilename LIKE '%wbem\\\wbemcomn.dll'
) a
ON LOWER(REVERSE(SPLIT(RelativeTargetName, '\'))[0]) = a.TargetFilename
WHERE LOWER(b.Channel) = 'security'
    AND b.EventID = 5145
    AND b.AccessMask = '0x2'
'''
)
df.show(10,False)
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|@timestamp             |Hostname                   |ShareName|SubjectUserName|SubjectLogonId|IpAddress  |IpPort|RelativeTargetName                |
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|2020-10-09 17:34:28.926|WORKSTATION6.theshire.local|\\*\C$   |pgustavo       |0x227a012     |172.18.39.5|50963 |Windows\System32\wbem\wbemcomn.dll|
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+

Analytic III

Look for C:\Windows\System32\wbem\wbemcomn.dll being accessed over the network with write (0x2) access mask via an administrative share (i.e C$) and created by the System process on the target system.

Data source

Event Provider

Relationship

Event

File

Microsoft-Windows-Security-Auditing

User accessed File

5145

File

Microsoft-Windows-Sysmon/Operational

Process created File

11

df = spark.sql(
'''
SELECT `@timestamp`, Hostname, ShareName, SubjectUserName, SubjectLogonId, IpAddress, IpPort, RelativeTargetName
FROM mordorTable b
INNER JOIN (
    SELECT LOWER(REVERSE(SPLIT(TargetFilename, '\'))[0]) as TargetFilename
    FROM mordorTable
    WHERE Channel = 'Microsoft-Windows-Sysmon/Operational'
        AND Image = 'System'
        AND EventID = 11
        AND TargetFilename LIKE '%wbem\\\wbemcomn.dll'
) a
ON LOWER(REVERSE(SPLIT(RelativeTargetName, '\'))[0]) = a.TargetFilename
WHERE LOWER(b.Channel) = 'security'
    AND b.EventID = 5145
    AND b.AccessMask = '0x2'
'''
)
df.show(10,False)
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|@timestamp             |Hostname                   |ShareName|SubjectUserName|SubjectLogonId|IpAddress  |IpPort|RelativeTargetName                |
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|2020-10-09 17:34:28.926|WORKSTATION6.theshire.local|\\*\C$   |pgustavo       |0x227a012     |172.18.39.5|50963 |Windows\System32\wbem\wbemcomn.dll|
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+

Analytic IV

Look for C:\Windows\System32\wbem\wbemcomn.dll being accessed over the network with write (0x2) access mask via an administrative share (i.e C$), created by the System process and loaded by the WMI provider host (wmiprvse.exe). All happening on the target system.

Data source

Event Provider

Relationship

Event

File

Microsoft-Windows-Security-Auditing

User accessed File

5145

File

Microsoft-Windows-Sysmon/Operational

Process created File

11

File

Microsoft-Windows-Sysmon/Operational

Process loaded Dll

7

df = spark.sql(
'''
SELECT `@timestamp`, Hostname, ShareName, SubjectUserName, SubjectLogonId, IpAddress, IpPort, RelativeTargetName
FROM mordorTable d
INNER JOIN (
    SELECT LOWER(REVERSE(SPLIT(TargetFilename, '\'))[0]) as TargetFilename
    FROM mordorTable b
    INNER JOIN (
        SELECT ImageLoaded
        FROM mordorTable
        WHERE Channel = 'Microsoft-Windows-Sysmon/Operational'
            AND EventID = 7
            AND LOWER(Image) LIKE '%wmiprvse.exe'
            AND ImageLoaded LIKE '%wbem\\\wbemcomn.dll'
    ) a
    ON b.TargetFilename = a.ImageLoaded
    WHERE b.Channel = 'Microsoft-Windows-Sysmon/Operational'
        AND b.Image = 'System'
        AND b.EventID = 11
) c
ON LOWER(REVERSE(SPLIT(RelativeTargetName, '\'))[0]) = c.TargetFilename
WHERE LOWER(d.Channel) = 'security'
    AND d.EventID = 5145
    AND d.AccessMask = '0x2'
'''
)
df.show(10,False)
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|@timestamp             |Hostname                   |ShareName|SubjectUserName|SubjectLogonId|IpAddress  |IpPort|RelativeTargetName                |
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+
|2020-10-09 17:34:28.926|WORKSTATION6.theshire.local|\\*\C$   |pgustavo       |0x227a012     |172.18.39.5|50963 |Windows\System32\wbem\wbemcomn.dll|
+-----------------------+---------------------------+---------+---------------+--------------+-----------+------+----------------------------------+

Known Bypasses

Idea

Playbook

False Positives

None

Hunter Notes

  • Baseline your environment to identify normal activity. Document all accounts creating files over the network via administrative shares.

  • Baseline wmiprvse execution and modules loaded (i.e signed and un-signed)

References

  • https://docs.microsoft.com/en-us/windows/win32/wmisdk/about-wmi