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BKDR_DASERF.ZBEI-A

October 20, 2017
 ALIASES:

Trojan.Win32.Daserf.e (Kaspersky); Backdoor:Win32/Nioupale.A (Microsoft); Backdoor.Trojan (Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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

It executes commands from a remote malicious user, effectively compromising the affected system. It does not have any backdoor routine.

It steals certain information from the system and/or the user.

It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

40,960 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

23 Apr 2013

Payload:

Compromises system security, Steals information, Downloads files, Connects to URLs/IPs

Arrival Details

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

  • %Program Files%\Common Files\System\Library\msid.dat - If administrator
  • %User Profile%\System\Library\msid.dat - If non-administrator

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It drops the following copies of itself into the affected system:

  • %Program Files%\Common Files\System\Library\mshost.exe - If administrator
  • %User Profile%\System\Library\mshost.exe - If non-administrator

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • mdwkkggs_mini

It injects itself into the following processes as part of its memory residency routine:

  • explorer.exe

Autostart Technique

This Backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\mdwkkggs_mini
DisplayName = "Local Resource Storage Service"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\mdwkkggs_mini
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\mdwkkggs_mini
ImagePath = "%Program Files%\Common Files\System\Library\mshost.exe"

It adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
mdwkkggs_mini = "%User Profile%\System\Library\mshost.exe" - If non-administrator

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

  • Create or terminate processes
  • Perform Remote Shell
  • Install Services
  • Start Services
  • Delete Services
  • Enumerate all drives with corresponding drive types
  • Enumerate files and directories
  • Open, Create, or Delete Files

It does not have any backdoor routine.

Information Theft

This Backdoor steals the following information:

  • Computer Name
  • System Default Language ID
  • OS Version
  • Is administrator
  • Is 64-bit

Other Details

This Backdoor connects to the following website to send and receive information:

  • http://phot.{BLOCKED}svsolu.com/kyobo/addr.gif
  • http://psfir.{BLOCKED}flame.com/images/addr.gif

However, as of this writing, the said sites are inaccessible.

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

13.672.05

FIRST VSAPI PATTERN DATE:

21 Sep 2017

VSAPI OPR PATTERN File:

13.673.00

VSAPI OPR PATTERN Date:

22 Sep 2017

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 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\ControlSet001\Services
    • mdwkkggs_mini

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • mdwkkggs_mini = "%User Profile%\System\Library\mshost.exe"

Step 6

Search and delete this file

[ 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.
  • %User Profile%\System\Library\msid.dat - If non-administrator
  • %Program Files%\Common Files\System\Library\msid.dat - If administrator

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_DASERF.ZBEI-A. 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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