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WORM_UPDATER.AC

January 20, 2014
 ALIASES:

Worm:Win32/Networm.A (Microsoft), W32/Updater.I@mm (Fortinet), Email-Worm.Win32.Atak (Ikarus), Win32/Pepex.I worm (ESET)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

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

  TECHNICAL DETAILS

File Size:

42,496 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

26 Dec 2013

Arrival Details

This worm arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It may arrive via network shares.

Installation

This worm drops the following copies of itself into the affected system and executes them:

  • C:\WINNT\Isass.exe
  • C:\WINDOWS\Isass.exe

It drops the following files:

  • %Windows%\stm8.inf

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

Autostart Technique

This worm registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr
Start = "3"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr
ErrorControl = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr
ImagePath = "C:\WINDOWS\Isass.exe" or "C:\WINNT\Isass.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr
DisplayName = "Windows Genuine Updater"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr\Security
Security = "{hex values}"

It adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Local Security Authority Process = "{malware path and file name} %1"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wgautr

Propagation

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

Other Details

This worm connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.65.27
  • {BLOCKED}.{BLOCKED}.67.26
  • {BLOCKED}.{BLOCKED}.73.27
  • {BLOCKED}.{BLOCKED}.68.27
  • {BLOCKED}.{BLOCKED}.133.26
  • {randomly generated IP address}

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.498.04

FIRST VSAPI PATTERN DATE:

26 Dec 2013

VSAPI OPR PATTERN File:

10.499.00

VSAPI OPR PATTERN Date:

27 Dec 2013

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • wgautr

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Local Security Authority Process = "{malware path and file name} %1"

Step 5

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.
  • %Windows%\stm8.inf

Step 6

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