Analysis by: Bren Matthew Ebriega
ALIASES:

Backdoor:MSIL/Quasar.GG!MTB (MICROSOFT); HEUR:Trojan.MSIL.Quasar.gen (KASPERSKY)

 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 connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 514,048 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 11 Apr 2021
Payload: Connects to URLs/IPs, Adds processes

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:

  • %Application Data%\Java\java.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:

  • %Application Data%\Java\java.exe
  • schtasks /create /tn "Java Client Startup" /sc ONLOGON /tr %Application Data%\Java\java.exe /rl HIGHEST /f

(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 creates the following folders:

  • %Application Data%\Java\

(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 mutexes to ensure that only one of its copies runs at any one time:

  • Local\aeed8d2a-e9e5-41aa-8bf5-368505b65ec2

Backdoor Routine

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

  • Update Self
  • Uninstall Self
  • Manage Files/Directories (Create, Delete, Upload, Download, Execute, List Drives, etc.)
  • Manage Registry (Edit, Query, etc.)
  • Manage Processes (Start, Stop, List Processes)
  • Manage StartupItems (Add, Remove, List)
  • System Power Commands (Shutdown, Restart, Standby/Suspend)
  • Remote Desktop (Control Mouse or Keyboard, View Desktop, List Monitors)
  • Remote Shells (Execute Arbitrary Shell Commands)
  • Reverse Proxy
  • Gather System Information:
    • Processor Info (CPU)
    • Memory Info (RAM)
    • Video Card Info (GPU)
    • Username
    • Computer Name
    • Domain Name
    • Host Name
    • System Drive
    • System Directory
    • Uptime
    • MAC Address
    • Local IP Address
    • Public IP Address
    • Antivirus
    • Firewall
    • Timezone
    • Country
  • Gather Credentials from Applications:
    • Common Browsers:
      • Chrome
      • Firefox
      • Internet Explorer
      • Opera
      • Yandex
    • Ftp Clients:
      • FileZilla
      • WinScp
  • Take Screenshot
  • Send Keylogger Data
  • Visit Websites

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

  • {BLOCKED}.{BLOCKED}.112.149:1337

Other Details

This Backdoor adds the following scheduled tasks:

  • Task Name: Java Client Startup
    Trigger: Logon of any user
    Task to be run: %Application Data%\Java\java.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).)

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.650.06
FIRST VSAPI PATTERN DATE: 11 Apr 2021
VSAPI OPR PATTERN File: 16.651.00
VSAPI OPR PATTERN Date: 12 Apr 2021

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.XXPE50FFF043

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

Restart in Safe Mode

[ Learn More ]

Step 5

Identify and terminate files detected as Backdoor.MSIL.QUASAR.P

[ 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 6

Deleting Scheduled Tasks

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

  • Task Name: Java Client Startup
    Task to be run: %Application Data%\Java\java.exe

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 7

Search and delete these folders

[ 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%\Java\

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.MSIL.QUASAR.P. 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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