WORM_NUQEL.AX

 Analysis by: Jasen Sumalapao

 ALIASES:

Worm:Win32/Nuqel.BB (Microsoft), PAK:UPX, ARC:Embedded, [script.au3]:Trojan.Win32.Autoit.zu (Kaspersky), W32.Imaut (Symantec), W32/YahLover.worm.gen (NAI), Mal/Tiotua-F, Mal/Tiotua-F (Sophos), Trojan.Win32.AutoIT.gen (v) (Sunbelt), TR/Dropper.Gen (Antivir), W32/MalwareS.AZSL (Authentium), Trojan.AutoIt.TQ (Bitdefender), PUA.Win32.Packer.Upx-53 (Clamav), W32/YahLover!worm (Fortinet), W32/MalwareS.AZSL (exact) (Fprot), Trojan.Win32.Agent (Ikarus), Win32/Virut.NBP virus (NOD32), New unknown virus W32/Obfuscated.H2!genr (Norman), Trojan.Autoit.F (VBA32)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Via physical/removable drives, Propagates via network shares

This worm arrives by connecting affected removable drives to a system. It arrives by accessing affected shared networks. It 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 uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

It disables Task Manager, Registry Editor, and Folder Options. It deletes autostart registry entries associated with the processes it terminates to completely disable applications.

It propagates via shared networks and drops copies of itself into available networks.

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

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

307,200 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Sep 2012

Payload:

Compromises system security

Arrival Details

This worm arrives by connecting affected removable drives to a system.

It arrives by accessing affected shared networks.

It 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 a copy of itself in the following folders using different file names:

  • %Windows%\IEXPLORER.EXE
  • %System%\IEXPLORER.EXE
  • %System%\WORD.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It drops the following component file(s):

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

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

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

It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

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
Yahoo Messengger = "%System%\IEXPLORER.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 IEXPLORER.exe"

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

The scheduled task executes the malware at the following period:

  • Everyday at 09:00

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
GlobalUserOffline = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
AtTaskMaxHours = "0"

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 = "1"

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NofolderOptions = "1"

It deletes autostart registry entries associated with the processes it terminates to completely disable applications.

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Minimal\
{4D36E967-E325-11CE-BFC1-08002BE10318}
{default} = "DiskDrive"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Network\
{4D36E967-E325-11CE-BFC1-08002BE10318}
{default} = "DiskDrive"

File Infection

This worm propagates via shared networks and drops copies of itself into available networks.

Propagation

This worm drops copies of itself in the following shared folders:

  • game_y.exe

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

  • Bi mat.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]
Open=IEXPLORER.exe
Shellexe cute=IEXPLORER.exe
Shell\Open\command=IEXPLORER.exe
Shell=Open

Backdoor Routine

This worm connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}.{BLOCKED}.128.132:80

Download Routine

This worm connects to the following website(s) to download and execute a malicious file:

  • http://setting.{BLOCKED}b.com/setting.doc
  • http://hvaonline.com.{BLOCKED}pages.com/setting.doc
  • http://setting3.{BLOCKED}5.com/setting.doc

As of this writing, the said sites are inaccessible.

Other Details

This worm does the following:

  • Disable Security feature by deleting Registry keys
  • Disable Rebooting through Safe Mode
  • Downloads and Executes other malicious files

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.396.02

FIRST VSAPI PATTERN DATE:

14 Sep 2012

VSAPI OPR PATTERN File:

9.397.00

VSAPI OPR PATTERN Date:

15 Sep 2012

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

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.

Step 4

Search and delete these files

[ Learn More ]
There may be some component 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.
  • %Windows%\setting.ini
  • %System%\autorun.ini
  • %Windows%\Tasks\At1.job

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\Microsoft\Windows\CurrentVersion\Run
    • Yahoo Messengger = "%System%\IEXPLORER.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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe IEXPLORER.exe"
      To: Shell = Explorer.exe

Step 7

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\Internet Settings
    • GlobalUserOffline = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • AtTaskMaxHours = "0"

Step 8

Restoring Deleted Registry Keys

  1. Still in Registry Editor, in the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>
    Control>SafeBoot>Minimal
  2. Right-click on the key and choose New>Key. Change the value of the new key to:
    {4D36E967-E325-11CE-BFC1-08002BE10318}
  3. Right-click on the value name and choose Modify. Change the value data of this entry to:
    DiskDrive
  4. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>
    Control>SafeBoot>Network
  5. Right-click on the key and choose New>Key. Change the value of the new key to:
    {4D36E967-E325-11CE-BFC1-08002BE10318}
  6. Right-click on the value name and choose Modify. Change the value data of this entry to:
    DiskDrive
  7. Close Registry Editor.

Step 9

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

[ Learn More ]
[Autorun] Open=IEXPLORER.exe Shellexe cute=IEXPLORER.exe Shell\Open\command=IEXPLORER.exe Shell=Open

Step 10

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