Analysis by: Warren Adam Sto. Tomas

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • 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 may be downloaded by other malware/grayware/spyware from remote sites.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 186,880 bytes
Memory Resident: Yes
Initial Samples Received Date: 09 Jan 2020
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.

It may be downloaded by other malware/grayware/spyware from remote sites.

Installation

This Backdoor drops the following files:

  • %ProgramData%\Microsoft\{random characters}.txt <- JavaScript used to execute the other .txt dropped file
  • %ProgramData%\Microsoft\{random characters}.txt <- contains malicious XSL backdoor script

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit), XP.)

It drops the following non-malicious file:

  • %ProgramData%\Microsoft\msxsl.exe

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit), XP.)

It adds the following processes:

  • %ProgramData%\Microsoft\msxsl.exe {filename of XSL backdoor script}.txt {filename of XSL backdoor script}.txt

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit), XP.)

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Notepad
{Computer name} = {scheduled task name},{filename of XSL backdoor script},{filename of JavaScript file}

Backdoor Routine

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

  • d&exec - download and execute PE file
  • more_eggs - update itself
  • gtfo - uninstall itself
  • more_onion - execute additional script
  • more_power - execute arbitrary commands

It connects to the following websites to send and receive information:

  • https://drive.{BLOCKED}content.kz/drive/info

Information Theft

This Backdoor gathers the following data:

  • Computer Serial Number
  • Hardware Information
  • Volume Label and Volume Serial Number of %HOMEDRIVE%
  • List of AV Products Installed
  • User Name
  • Computer Name
  • OS Version
  • OS Product Type
  • OS Build
  • OS Architecture
  • IPv4 Address
  • Bot Version

Stolen Information

This Backdoor sends the gathered information via HTTP POST to the following URL:

  • https://drive.{BLOCKED}content.kz/drive/info

Other Details

This Backdoor connects to the following URL(s) to check for an Internet connection:

  • http://www.w3.org/1999/XSL/Format

It connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.8.8/{random string}

It does the following:

  • It will not execute its malicious routines if any of the following is not satisfied:
    • year is 2019
    • file extension of running malware process is .ocx
    • malware process is running as regsvr32.exe

It deletes itself after execution.

It adds the following scheduled tasks:

  • Task Name: {random characters}
  • Trigger: At system boot; executes indefinitely
  • Action: cscripT /B /e:jsCript {filename of JavaScript file}.txt

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.612.02
FIRST VSAPI PATTERN DATE: 10 Jan 2020
VSAPI OPR PATTERN File: 15.613.00
VSAPI OPR PATTERN Date: 11 Jan 2020

Step 1

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 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

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:  

  • {random characters} - cscripT /B /e:jsCript {filename of JavaScript file}.txt

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

Step 5

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.
  • %ProgramData%\Microsoft\{random characters}.txt
  • %ProgramData%\Microsoft\{random characters}.txt

Step 6

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\Microsoft\Notepad
    • {Computer name} = "{scheduled task name},{filename of XSL backdoor script},{filename of JavaScript file}"

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.TERRALOADER.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.


Did this description help? Tell us how we did.