WORM_SOHANAD.YTG

 Analysis by: Vincent Martin Hermosura

 ALIASES:

IM-Worm.Win32.Sohanad.pw (Kaspersky), Worm:Win32/Nuqel.BD (Microsoft), W32.Imaut.BH (Symmantec), W32/Autorun.worm.f (Mcafee), Worm.Win32.Nuqel.zb (v) (Sunbelt), TR/Patched.Ren.Gen (Antivir), W32/Trojan-Gypikon-based.DM2!Ma (Authentium), Gen:Trojan.Heur.AutoIT.2 (Bitdefender), W32/Sohanad.A!worm (Fortinet), W32/Trojan-Gypikon-based.DM2!Ma (Fprot), Worm.Win32.AutoIt (Ikarus), Win32/Autoit.AG worm, Win32/Autoit.AG worm (Esset), Trj/Autoit.gen (Panda), Trojan-Downloader.Autoit.gen (Vba32)

 PLATFORM:

Windows

 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:

Downloaded from the Internet, Dropped by other malware, Propagates via 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 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 Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

30 Sep 2014

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 copies of itself into the affected system:

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

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

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 Messsenger = "%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 at the following period:

    • everyday 9:00 AM

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
WorkgroupCrawler\Shares

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Schedule
AtTaskMaxHours = "0"

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\
Explorer
NofolderOptions = "0"

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

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

Propagation

This worm drops copies of itself in the following drives:

  • {Removable Drive Letter}:\New Folder .exe
  • {Removable Drive Letter}:\regsvr.exe
  • {Removable Drive Letter}:\{Folder Name}\{Folder Name}.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=regsvr.exe
Shellexecute=regsvr.exe
Shell\Open\command=regsvr.exe
Shell=Open

Dropping Routine

This worm drops the following files:

  • %System%\28463\svchost.001
  • %System%\setting.ini
  • %System%\setup.ini
  • %Windows%\At1.job
  • {Removable Drive Letter}:\autorun.inf

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

NOTES:

This malware uses the icon of a Microsoft Word document to trick the user into thinking it is a normal file.

  SOLUTION

Minimum Scan Engine:

9.700

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

Identify and delete files detected as WORM_SOHANAD.YTG using either the Startup Disk or Recovery Console

[ Learn More ]

Step 4

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 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\Policies
    • System
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler
    • Shares

Step 6

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
    • Msn Messsenger = %System%\regsvr.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Schedule
    • AtTaskMaxHours = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares
    • shared = \New Folder .exe

Step 7

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

Step 8

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.
  • %System%\28463

Step 9

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

Step 10

Search and delete AUTORUN.INF files created by WORM_SOHANAD.YTG that contain these strings

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

Step 11

Scan your computer with your Trend Micro product to delete files detected as WORM_SOHANAD.YTG. 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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