Trojan.MSIL.NEGASTEAL.DYSHRSKI
Trojan:Win32/Leonem (MICROSOFT)
Windows
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
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:
- %Application Data%\{Random characters}.exe → copy of itself with hidden and read-only attributes
- %User Temp%\tmp{Random characters}.tmp
- %User Temp%\{8 Random characters}.{3 Random characters}.ps1
- %User Temp%\{8 Random characters}.{3 Random characters}.psm1
- %AppDataLocal%\Microsoft\Windows\PowerShell\StartupProfileData-NonInteractive
- %Application Data%\yGbzOMp\yGbzOMp.exe → copy of itself
(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).. %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).. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local 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 "Updates\{Random characters}" /XML "%User Temp%\tmp{Random characters}.tmp"
- "%System%\WindowsPowerShell\v1.0\powershell.exe" Add-MpPreference -ExclusionPath "%Application Data%\{Random characters}.exe"
(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).. %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%\yGbzOMp
(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).)
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
yGbzOMp = %Application Data%\yGbzOMp\yGbzOMp.exe
Other System Modifications
This Trojan deletes the following files:
- %User Temp%\tmp{Random characters}.tmp
- %User Temp%\{8 Random characters}.{3 Random characters}.ps1
- %User Temp%\{8 Random characters}.{3 Random characters}.psm1
(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 adds the following scheduled tasks:
- Task name: Updates\{Random characters}
Task to be run: %Application Data%\{Random characters}.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
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.XXPE50FFF062
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
Step 5
Deleting Scheduled Tasks
The following {Task Name} - {Task to be run} listed should be used in the steps identified below:
- Task name: Updates\{Random characters}
Task to be run: %Application Data%\{Random characters}.exe
For Windows 2000, Windows XP, and Windows Server 2003:
- Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
System Tools>Scheduled Tasks. - Locate each {Task Name} values listed above in the Name column.
- Right-click on the said file(s) with the aforementioned value.
- Click on Properties. In the Run field, check for the listed {Task to be run}.
- 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:
- 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. - In the left panel, click Task Scheduler Library.
- In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
- In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
- If the said string is found, delete the task.
Step 6
Delete this registry value
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\Run
- yGbzOMp = %Application Data%\yGbzOMp\yGbzOMp.exe
- yGbzOMp = %Application Data%\yGbzOMp\yGbzOMp.exe
Step 7
Search and delete this file
- %Application Data%\{Random characters}.exe
- %User Temp%\tmp{Random characters}.tmp
- %User Temp%\{8 Random characters}.{3 Random characters}.ps1
- %User Temp%\{8 Random characters}.{3 Random characters}.psm1
- %AppDataLocal%\Microsoft\Windows\PowerShell\StartupProfileData-NonInteractive
- %Application Data%\yGbzOMp\yGbzOMp.exe
Step 8
Search and delete these folders
Step 9
Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.MSIL.NEGASTEAL.DYSHRSKI. 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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