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WORM_SILLY.D

October 09, 2012
 Analysis by: Rhena Inocencio
 ALIASES:

Worm:Win32/SillyShareCopy.D (Microsoft), Win32/AutoRun.HI worm (Symantec), Backdoor.Win32.Hupigon.fba (Kaspersky)

 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 via removable drives. 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 employs registry shell spawning by adding certain registry entries. This allows this malware to execute even when other applications are opened.

It drops copies of itself in all removable and physical drives found in the system. 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:

580,608 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Aug 2012

Arrival Details

This worm arrives via removable drives.

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 files:

  • %System%\Explorer.sm1

(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.)

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

  • %Windows%\System\services.exe

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

Autostart Technique

This worm employs registry shell spawning to ensure its execution when certain file types are accessed by adding the following entries:

HKEY_CLASSES_ROOT\sm1_Auto_File\shell\
open\command
(Default) = "%Windows%\System\services.exe %1"

HKEY_CLASSES_ROOT\sm1_Auto_File\shell\
open\command
(Default) = "%Windows%\System\services.exe %1"

Other System Modifications

This worm adds the following registry keys:

HKEY_CLASSES_ROOT\.sm1

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.sm1

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
AudioMan = "%System%\Explorer.sm1"

HKEY_CLASSES_ROOT\sm1_Auto_File
(Default) = "sm1_Auto_File"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.sm1
(Default) = "sm1_Auto_File"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

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

Propagation

This worm drops copies of itself in all removable and physical drives found in the system.

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

  SOLUTION

Minimum Scan Engine:

9.200

VSAPI OPR PATTERN File:

9.295.00

VSAPI OPR PATTERN Date:

01 Aug 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

Search and delete this file

[ 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%\Explorer.sm1

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_CLASSES_ROOT\sm1_Auto_File\shell\open\command
    • (Default) = "%Windows%\System\services.exe %1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\sm1_Auto_File\shell\open\command
    • (Default) = "%Windows%\System\services.exe %1"
  • In HKEY_CLASSES_ROOT\sm1_Auto_File
    • (Default) = "sm1_Auto_File"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.sm1
    • (Default) = "sm1_Auto_File"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • AudioMan = "%System%\Explorer.sm1"

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_CLASSES_ROOT
    • .sm1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • .sm1

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden = "1"

Step 7

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