Analysis by: John Anthony Banes
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

This Trojan may arrive bundled with malware packages as a malware component. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size: 142,336 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 09 May 2018
Payload: Connects to URLs/IPs, Drops files

Arrival Details

This Trojan may arrive bundled with malware packages as a malware component.

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

This malware arrives via the following means:

  • Microsoft Windows SMB Server (MS17-010) Vulnerability

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv\Parameters

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
Type = 16

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
Start = 2

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
ErrorControl = 1

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
ImagePath = %SystemRoot%\System32\svchost.exe -k netsvcs

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
DisplayName = Windows Modules Activations Services

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
ObjectName = LocalSystem

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv
Description = The Windows Modules Activations Services (WMAS) provides modules activation, resource management and health management services for message-activated applications.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\wmassrv\Parameters
ServiceDll = %System%\wmassrv.dll

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Svchost
netsvcs = {adds "wmassrv" to its existing data}

Download Routine

This Trojan connects to the following URL(s) to download its component file(s):

  • {local network IP address}

It saves the files it downloads using the following names:

  • %System%\EnrollCertXaml.dll - encrypted component

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other Details

This Trojan drops the following file(s)/component(s):

  • %System%\wmassrv.dll

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It does the following:

  • It may execute the following commands:
    • schtasks.exe /create /TN "\Microsoft\Windows\UPnP\{string}" /RU SYSTEM /TR "regsvr32 /s /u {string}" /SC ONSTART
    • schtasks.exe /create /TN "\Microsoft\Windows\UPnP\{string}" /RU SYSTEM /TR "rundll32 {string},ServiceCrtMain" /SC ONSTART
    • schtasks.exe /run /TN "\Microsoft\Windows\UPnP\%{string}"
  • This malware listens on TCP port 52137 to retrieve the components from host.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.270.04
FIRST VSAPI PATTERN DATE: 24 May 2018
VSAPI OPR PATTERN File: 14.271.00
VSAPI OPR PATTERN Date: 25 May 2018

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • Type = 16
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • ErrorControl = 1
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • ImagePath = %SystemRoot%\System32\svchost.exe -k netsvcs
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • DisplayName = Windows Modules Activations Services
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • ObjectName = LocalSystem
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • Description = The Windows Modules Activations Services (WMAS) provides modules activation, resource management and health management services for message-activated applications.
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv\Parameters
    • ServiceDll = %System%\wmassrv.dll

Step 5

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services
    • wmassrv
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmassrv
    • Parameters

Step 6

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Svchost
    • netsvcs = {added "wmassrv" entres to its data}

Step 7

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System%\EnrollCertXaml.dll
  • %System%\wmassrv.dll

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_WMINE.B. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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