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TROJ_NEUREVT.USQQ

August 04, 2017
 ALIASES:

HEUR:Trojan.Win32.Generic (Kaspersky); Trojan:Win32/Neurevt.AB (Microsoft); W32.Rontokbro@mm (Symantec)

 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.

It modifies registry entries to disable the Windows Firewall settings. This action allows this malware to perform its routines without being deteted by the Windows Firewall.

  TECHNICAL DETAILS

File Size:

200,704 bytes

File Type:

EXE

Initial Samples Received Date:

25 Jul 2017

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 copies of itself into the affected system:

  • %All Users Profile%\busa.exe
  • %All Users Profile%\Application Data\busa.exe (Windows XP)
  • %ProgramData%\folder\{random file name}.exe

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following files:

  • %User Temp%\z{3 random numbers} -> deleted afterwards
  • %Application Data%\Microsoft\Crypto\RSA\{random name}\{random file name2}
  • %ProgramData%\folder\desktop.ini -> deleted afterwards

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following processes:

  • %Windows%\explorer.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It creates the following folders:

  • %ProgramData%\folder
  • %Application Data%\Microsoft\Crypto\RSA\{random name}

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It is injected into the following processes running in memory:

  • %Windows%\explorer.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tasks\{random name2}
Path = "\Update\busa"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
adminkey = "%ProgramData%\folder\{random file name}.exe"

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Win7zip
Uuid = "{random data}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
{random file name}.exe
DisableExceptionChainValidation = " "

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
rstrui.exe
Debugger = “{random file name}.exe”

It modifies the following registry entries to disable the Windows Firewall settings:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
EnableFirewall = "0"

(Note: The default value data of the said registry entry is "1".)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\SharedAccess\Parameters\
FirewallPolicy\PublicProfile
EnableFirewall = "0"

(Note: The default value data of the said registry entry is "1".)

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:

  • windowsupdate.microsoft.com

It connects to the following possibly malicious URL:

  • {BLOCKED}raa.com
  • {BLOCKED}ree.com
  • {BLOCKED}ruu.com

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.560.01

FIRST VSAPI PATTERN DATE:

25 Jul 2017

VSAPI OPR PATTERN File:

13.561.00

VSAPI OPR PATTERN Date:

26 Jul 2017

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 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

Delete this registry value

[ Learn More ]

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
    • Adminkey = "%ProgramData%\folder\{random file name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\rstrui.exe
    • Debugger = “{random file name}.exe”

Step 5

Delete this registry key

[ Learn More ]

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
    • Win7zip
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks
    • {random name2}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • {random file name}.exe

Step 6

Restore this modified registry value

[ Learn More ]

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_LOCAL_MACHINE\SYSTEM\ControlSet001\services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
    • From: EnableFirewall = “0”
      To: EnableFirewall = “1”
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\SharedAccess\Parameters\FirewallPolicy\PublicProfile
    • From: EnableFirewall = “0”
      To: EnableFirewall = “1”

Step 7

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.
  • %ProgramData%\folder
  • %Application Data%\Microsoft\Crypto\RSA\{random name}

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_NEUREVT.USQQ . 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.

NOTES:
Before doing Solution steps 5 and 7, ensure that permission to the contents of the folder and the registry keys is added by giving full control to Everyone.


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