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WORM_SOHANAD.UN

October 09, 2012
 Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives by connecting affected removable drives to a system. 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 the Windows Task Scheduler to add a scheduled task that executes the copies it drops.

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:

382,071 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

12 Oct 2011

Arrival Details

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

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 the following copies of itself into the affected system:

  • %Windows%\SSCVIHOST.exe
  • %System%\blastclnnn.exe
  • %System%\SSCVIHOST.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 file(s)/component(s):

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

(Note: %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.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.

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%\SSCVIHOST.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 SSCVIHOST.exe"

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

The scheduled task executes the malware every:

  • 9:00 am

Other System Modifications

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

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

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
NextAtJobId = "2"

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

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"

Propagation

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

  • New Folder.exe
  • SSCVIHOST.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=SSCVIHOST.exe
Shellexe cute=SSCVIHOST.exe
Shell\Open\command=SSCVIHOST.exe
Shell=Open

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.490.02

FIRST VSAPI PATTERN DATE:

12 Oct 2011

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

Identify and terminate files detected as WORM_SOHANAD.UN

[ Learn More ]
  1. 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.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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

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
    • Yahoo Messengger = %System%\SSCVIHOST.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • AtTaskMaxHours = 0

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 SSCVIHOST.exe
      To: Shell = Explorer.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • From: NextAtJobId = 2
      To: NextAtJobId = 1

Step 6

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

Step 7

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

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

Step 8

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