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Backdoor.Win32.BUER.A

February 07, 2020
 Analysis by: Paul Steven Nadera
 ALIASES:

Backdoor.Win32.Androm.tejf (Kaspersky); Trojan:Win32/Ursnif.A!MTB (Microsoft); Win32/Spy.Ursnif.CU trojan (NOD32);)

 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:

Dropped by other malware, Downloaded from the Internet


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 then deletes itself afterward.

It executes commands from a remote malicious user, effectively compromising the affected system.

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

  TECHNICAL DETAILS

File Size:

638,976 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

29 Dec 2019

Payload:

Connects to URLs/IPs, Steals information

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 copies of itself into the affected system and executes them:

  • %Application Data%\ActiveX\manager.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • {Malware Path}\{Malware Name}.exe
  • %Application Data%\ActiveX\manager.exe "%User Temp%\059a1c87b0d2cb1f41588f7b81b7b569be204b57.exe" ensgJJ

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %Application Data%\ActiveX

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It executes then deletes itself afterward.

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

  • jf2QmcP51Kse9aMfj

Autostart Technique

This Backdoor modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
ActiveX Component = %Application Data%\ActiveX\manager.exe

Backdoor Routine

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

  • Update itself
  • Download and execute a malicious file

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}.{BLOCKED}.247.177:8080

As of this writing, the said servers are currently inaccessible.

Information Theft

This Backdoor steals the following information:

  • Windows Version
  • Processor Architecture
  • Number of Processors
  • User Privilege

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.542.08

FIRST VSAPI PATTERN DATE:

06 Dec 2019

VSAPI OPR PATTERN File:

15.543.00

VSAPI OPR PATTERN Date:

07 Dec 2019

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    Troj.Win32.TRX.XXPE50FFF033

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Identify and terminate files detected as Backdoor.Win32.BUER.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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\RunOnce
    • ActiveX Component = "%Application Data%\ActiveX\manager.exe"

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result. %Application Data%\ActiveX\

Step 7

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


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