WORM_NUQEL.BL

September 07, 2013
 Analysis by: Rika Joi Gregorio
 Modified by: Jaime Benigno Reyes
 ALIASES:

Worm:Win32/Nuqel.BD(Microsoft), W32/Autorun.worm.f(McAfee), W32.Imaut.BH(Norton), W32/Sohanad.A!worm(Fortinet), Win32/Autoit.AG worm(Eset)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Via physical/removable drives

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It disables Task Manager, Registry Editor, and Folder Options.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size:

6,511,616 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Jul 2013

Payload:

Connects to URLs/IPs

Arrival Details

This worm 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 worm drops the following component file(s):

  • %Windows%\Tasks\At1.job
  • %System%\28463\svchost.001
  • %System%\setting.ini
  • %System%\setup.ini

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

It drops the following copies of itself into the affected system:

  • %Windows%\regsvr.exe
  • %System%\regsvr.exe
  • %System%\svchost .exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It creates the following folders:

  • %System%\28463

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Msn Messenger = "%System%\regsvr.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe regsvr.exe"

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

The scheduled task executes the malware every:

  • 9:00 AM, everyday

Other System Modifications

This worm adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
WorkgroupCrawler\Shares
shared = "\New Folder .exe"

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NofolderOptions = "0"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {Drive Letter}:\New Folder .exe
  • {Drive Letter}:\regsvr.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[Autorun]
Shell\Open\command=regsvr.exe
Shell=Open
Open=regsvr.exe
Shellexecute=regsvr.exe

NOTES:

This worm searches for folders in all removable drives then drops copies of itself inside the folder as {folder name}.EXE.

This worm connects to the following URLs to download files:

  • http://yahoo.com/setting.doc
  • http://www.yahoo.com/setting.doc
  • http://www.yahoo.com/setting.xls

However, the said files do not exist.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.174.04

FIRST VSAPI PATTERN DATE:

24 Jul 2013

VSAPI OPR PATTERN File:

10.175.00

VSAPI OPR PATTERN Date:

25 Jul 2013

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

Restart in Safe Mode

[ Learn More ]

Step 3

Enable Registry Editor, Task Manager, and Folder options

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware/spyware.

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\Explorer\WorkgroupCrawler\Shares
    • shared = "\New Folder .exe"

Step 5

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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe regsvr.exe"
      To: Shell = "Explorer.exe"

Step 6

Search and delete these folders

[ 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.
  • %System%\28463

Step 7

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.
  • %System%\setting.ini
  • %System%\setup.ini
  • %Windows%\Tasks\At1.job

Step 8

Search and delete AUTORUN.INF files created by WORM_NUQEL.BL that contain these strings

[ Learn More ]


[Autorun]
Open=regsvr.exe
Shellexecute=regsvr.exe
Shell\Open\command=regsvr.exe
Shell=Open

Step 9

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