TROJ_DLOADER.OZB

March 16, 2013
 ALIASES:

TrojanDropper:Win32/Vbegg.A (Microsoft); Backdoor.Graybird (Symantec); Trojan-Dropper.Win32.Dapato.bzzh (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse SHeur4.AZHD (AVG)

 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.

It disables Task Manager, Registry Editor, and Folder Options.

  TECHNICAL DETAILS

File Size:

163,328 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

31 Jan 2013

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\{110E25E1-8103-4368-8662-B1188985D70A}

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run

HKEY_CLASSES_ROOT\CLSID\{110E25E1-8103-4368-8662-B1188985D70A}

HKEY_CLASSES_ROOT\CLSID\{110E25E1-8103-4368-8662-B1188985D70A}\
InprocServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Ext\
PreApproved\{110E25E1-8103-4368-8662-B1188985D70A}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{110E25E1-8103-4368-8662-B1188985D70A}\InprocServer32
ThreadingModel = "Apartment"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Ext\CLSID
{110E25E1-8103-4368-8662-B1188985D70A} = "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\
Explorer\Run
SecurityCRT = "Wscript.exe %User Profile%\Application Data\certificate.vbs"

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\syslog.txt
  • %User Profile%\0
  • %User Temp%\31.tmp
  • %User Profile%\ssl.dll
  • %User Profile%\Application Data\certificate.vbs

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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

Close all opened browser windows

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/spyware.

Step 4

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_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • Run
  • In HKEY_CLASSES_ROOT\CLSID
    • {110E25E1-8103-4368-8662-B1188985D70A}
  • In HKEY_CLASSES_ROOT\CLSID\{110E25E1-8103-4368-8662-B1188985D70A}
    • InprocServer32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Ext\PreApproved
    • {110E25E1-8103-4368-8662-B1188985D70A}

Step 5

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\{110E25E1-8103-4368-8662-B1188985D70A}\InprocServer32
    • ThreadingModel = "Apartment"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Ext\CLSID
    • {110E25E1-8103-4368-8662-B1188985D70A} = "1"

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.
  • %User Profile%\syslog.txt
  • %User Profile%\0
  • %User Temp%\31.tmp
  • %User Profile%\ssl.dll
  • %User Profile%\Application Data\certificate.vbs

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_DLOADER.OZB. 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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