ALIASES:

TrojanDownloader:Win32/Zlob (Microsoft); Trojan.Zlob (Symantec); Trojan-Downloader.Win32.Zlob.kj (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan.Startpage.JF (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

Tipo de compactação: 98,304 bytes
Tipo de arquivo: EXE
Residente na memória: No
Data de recebimento das amostras iniciais: 09 Dec 2012

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Autostart Technique

This Trojan registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{4da4616d-7e6e-4fd9-a2d5-b6c535733e22}

Other System Modifications

This Trojan deletes the following files:

  • %Program Files%\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It adds the following registry keys:

HKEY_CLASSES_ROOT\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}

HKEY_CLASSES_ROOT\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}\
InprocServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
explorer\run

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objecta\{4da4616d-7e6e-4fd9-a2d5-b6c535733e22}

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Search

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}\InprocServer32
ThreadingModel = "Apartment"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
explorer\run
nvctrl.exe = "nvctrl.exe"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = "about:blank"

(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome.)

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}

Dropping Routine

This Trojan drops the following files:

  • %System%\hp87AE.tmp
  • %System%\ncompat.tlb
  • %System%\interf.tlb

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

This report is generated via an automated analysis system.

  SOLUTION

Mecanismo de varredura mínima: 9.300

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

Close all opened browser windows

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_CLASSES_ROOT\CLSID
    • {4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}
  • In HKEY_CLASSES_ROOT\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}
    • InprocServer32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\explorer
    • run
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objecta
    • {4da4616d-7e6e-4fd9-a2d5-b6c535733e22}
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
    • Search

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\Classes\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}\InprocServer32
    • ThreadingModel = "Apartment"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\explorer\run
    • nvctrl.exe = "nvctrl.exe"

Step 5

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\Internet Explorer\Main
    • From: Start Page = "about:blank"
      To: Start Page = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome""

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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%\hp87AE.tmp
  • %System%\ncompat.tlb
  • %System%\interf.tlb

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_ZLOB.JW. 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.

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %Program Files%\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll

Step 9

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • {18DF081C-E8AD-4283-A596-FA578C2EBDC3}


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