WORM_IMAUT.SME

 Analysis by: Michael Cabel
 Modified by: Kathleen Notario

 ALIASES:

Virus:Win32/Lopown.B (Microsoft)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via instant messaging applications

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

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names. The sent messages contains a link where a copy of the malware may be downloaded.

  TECHNICAL DETAILS

File Size:

204,800 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Nov 2011

Arrival Details

This worm 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 the following non-malicious files:

  • %Windows%\wininit.ini
  • %System%\Xpen.dat
  • %System%\Penx.dat

(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:

  • %System%\config\Win.exe
  • %Windows%\system\Fun.exe
  • %Windows%\inf\Other.exe
  • %Windows%\Help\Other.exe
  • %System%\WinSit.exe
  • %Windows%\dc.exe
  • %Windows%\SVIQ.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 uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

It injects itself into the following processes as part of its memory residency routine:

  • lsass.exe
  • csrss.exe
  • svchost.exe

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
imscmig = "%Windows%\imscmig.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
dc2k5 = "%Windows%\SVIQ.EXE"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Fun = "%Windows%\system\Fun.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
dc = "%Windows%\dc.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
run = "%System%\config\Win.exe

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
load = %Windows%\inf\Other.exe

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = Explorer.exe %System%\WinSit.exe

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

Propagation

This worm drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

The sent messages contain the following link(s), where a copy of the malware may be downloaded:

  • http://{BLOCKED}ivb.googlepages.com/ND.txt

It sends messages that contain links to sites hosting remote copies of itself using the following instant-messaging (IM) applications:

  • Yahoo Messenger

NOTES:

It drops the following copy of itself into network shares:

  • Fun.exe

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

currently processing (rename)

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

Identify and delete files detected as WORM_IMAUT.SME using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

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
    • imscmig = %Windows%\imscmig.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • dc2k5 = %Windows%\SVIQ.EXE
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Fun = %Windows%\system\Fun.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • dc = %Windows%\dc.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • run = %System%\config\Win.exe

Step 4

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_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • From: load = %Windows%\inf\Other.exe
      To: load =
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = Explorer.exe %Windows%system32\WinSit.exe
      To: Shell = Explorer.exe

Step 5

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.

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_IMAUT.SME. 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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