ALIASES:

Trojan.Win32.Fsysna.fztx (Kaspersky)

 PLATFORM:

Windows

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

  • 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: 7,371,776 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 12 Feb 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 icacls "%Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80" /inheritance:e /deny "*S-1-1-0:(R,REA,RA,RD)" & icacls "%Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80" /inheritance:e /deny "*S-1-5-7:(R,REA,RA,RD)" & icacls "%Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80" /inheritance:e /deny "{username}:(R,REA,RA,RD)"
  • taskeng.exe {ED7BEC3C-D9D8-4F1A-A775-5279D38DFFD1} S-1-5-21-2407829820-1079796033-203259571-500:{computername}\{username}:Interactive:[1]
  • icacls "%Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80" /inheritance:e /deny "*S-1-1-0:(R,REA,RA,RD)"
  • icacls "%Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80" /inheritance:e /deny "*S-1-5-7:(R,REA,RA,RD)"
  • icacls "%Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80" /inheritance:e /deny "{username}:(R,REA,RA,RD)"
  • %Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80\lsass.exe %Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80\lsass.exe
  • %System%\svchost.exe -k WerSvcGroup

(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%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80

(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).)

Other System Modifications

This Trojan deletes the following files:

  • {malware file path and name}

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\BITS
Start = "3"

(Note: The default value data of the said registry entry is 3.)

Dropping Routine

This Trojan drops the following files:

  • %Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80\lsass.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).)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}er.com

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.850

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

Identify and terminate files detected as Trojan.Win32.FSYSNA.AI

[ 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 3

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\BITS
    • From: Start = "3"
      To: Start = ""3""

Step 4

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.
  • %Application Data%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80\lsass.exe

Step 5

Search and delete this folder

[ 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%\amd64_microsoft-windows-comdlg32.resources_31bf3856ad364e35_10.0.14393.2636_zh-cn_c005df2cb1ca3c80

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.FSYSNA.AI. 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 the following Trend Micro Support pages for more information:

Step 7

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • {malware file path and name}


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