Trojan.Win32.SHELMA.AMC

 Analysis by: Maureen Reyes

 ALIASES:

Trojan:Win32/Skeeyah.A!bit (MIcrosoft), Trojan-Downloader.Win32.Agentb.i (Kaspersky)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan 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:

4,887,552 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

28 Dec 2018

Arrival Details

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

Installation

This Trojan drops the following files:

  • %Program Files%\Common Files\xpwpd.dat
  • %System%\wpd.dat
  • %System%\csrs.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), 7 (32-bit), and 8 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), 7 (64-bit), and 8 (64-bit).. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It adds the following processes:

  • taskkill /f /im csrs.exe
  • sc stop netprofm
  • sc config netprofm start= disabled
  • sc stop NaSvc
  • sc config NlaSvc start= disabled
  • net stop WinNsaSrv
  • sc config WinNsaSrv start= disabled
  • sc stop 1MpsSvc
  • sc config 1MpsSvc start= disabled

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
DownloadManager

HKEY_LOCAL_MACHINE\Software\Description

HKEY_LOCAL_MACHINE\Software\Description\
Microsoft

HKEY_LOCAL_MACHINE\Software\Description\
Microsoft\Rpc

HKEY_LOCAL_MACHINE\Software\Description\
Microsoft\Rpc\UuidTemporaryData

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Description\
Microsoft\Rpc\UuidTemporaryData
NetworkAddress = "{Hex Data}"

HKEY_LOCAL_MACHINE\Software\Description\
Microsoft\Rpc\UuidTemporaryData
NetworkAddressLocal = "0"

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}p.{BLOCKED}p.org
  • {BLOCKED}.{BLOCKED}.{BLOCKED}.174.csrs.exe

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.744.04

FIRST VSAPI PATTERN DATE:

11 Jan 2019

VSAPI OPR PATTERN File:

14.745.00

VSAPI OPR PATTERN Date:

12 Jan 2019

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

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\Software\Description\Microsoft\Rpc\UuidTemporaryData
    • NetworkAddress = "{Hex Data}
  • In HKEY_LOCAL_MACHINE\Software\Description\Microsoft\Rpc\UuidTemporaryData
    • NetworkAddressLocal = "0"

Step 4

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\Software\Microsoft
    • DownloadManager
  • In HKEY_LOCAL_MACHINE\Software\Description\Microsoft\Rpc
    • UuidTemporaryData
  • In HKEY_LOCAL_MACHINE\Software\Description\Microsoft
    • Rpc
  • In HKEY_LOCAL_MACHINE\Software\Description
    • Microsoft
  • In HKEY_LOCAL_MACHINE\Software
    • Description

Step 5

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.
  • %Program Files%\Common Files\xpwpd.dat
  • %System%\wpd.dat
  • %System%\csrs.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.SHELMA.AMC. 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 the following Trend Micro Support pages for more information:


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