Analysis by: Jay Garcia
ALIASES:

Trojan-Dropper.PowerShell.Compressed.a (Kaspersky); Virus.PowerShell.Obfuscator (Ikarus)

 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: 3,425 bytes
Memory Resident: Yes
Initial Samples Received Date: 21 Oct 2019

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 drops the following files:

  • %User Temp%\{random characters}.{random characters}.ps1
  • %User Temp%\{random characters}.{random characters}.psm1
  • %User Temp%\tempfle.txt
  • %User Temp%\{random characters}.txt

(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 adds the following processes:

  • "%System%\schtasks.exe" /create /tn {random characters} /xml %User Temp%\tempfle.txt /F
  • "%System%\schtasks.exe" /run /tn {random characters}
  • "%System%\schtasks.exe" /create /tn {random characters}\{random characters} /xml %User Temp%\tempfle.txt /F
  • "%System%\schtasks.exe" /run /tn {random characters}\{random characters}

(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).)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://t.{BLOCKED}2.com/v.js
  • http://t.{BLOCKED}y.com/v.js
  • http://down.{BLOCKED}g.com/wf.cab
  • http://t.{BLOCKED}a.com/v.js

It adds the following scheduled tasks:

  • Task Name: {random characters}
    Trigger: Every hour
    Task to be run: cmd /c "set A=power& call %A%shell -ep bypass -e {base64 encoded script}"
  • Task Name: {random characters}\ {random characters}
    Trigger: Every hour
    Task to be run: cmd /c "set A=power& call %A%shell -ep bypass -e {base64 encoded script}"

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.446.03
FIRST VSAPI PATTERN DATE: 22 Oct 2019
VSAPI OPR PATTERN File: 15.447.00
VSAPI OPR PATTERN Date: 23 Oct 2019

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} - cmd /c "set A=power& call %A%shell -ep bypass -e {base64 encoded script}"
  • {random characters}\{random characters} - cmd /c "set A=power& call %A%shell -ep bypass -e {base64 encoded script}"

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.  
  • %User Temp%\{random characters}.{random characters}.ps1
  • %User Temp%\{random characters}.{random characters}.psm1
  • %User Temp%\tempfle.txt
  • %User Temp%\{random characters}.txt

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.PS1.POWLOAD.JKF. 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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