TROJ_AMBLER.WJ

October 24, 2012
 Analysis by: Sabrina Lei Sioting
 ALIASES:

Worm:Win32/Ambler.A (Microsoft), Trojan-Spy.Win32.Amber.ut (Kaspersky), TR/Spy.Amber.UT (Antivir), W32/Ambler.BM!tr (Fortinet), Trojan-Spy.Win32.Amber (Ikarus),

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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

File Size:

52,245 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Apr 2010

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 adds the following registry keys to install itself as a Browser Helper Object (BHO):

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CLASSES_ROOT\CLSID\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}
{default} = "Internet Explorer Plugin"

HKEY_CLASSES_ROOT\CLSID\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}\
InprocServer32
{default} = "tftb71.dll"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Enable Browser Extensions = "yes"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}
{default} = "Internet Explorer Plugin"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}\InprocServer32
{default} = "tftb71.dll"

It adds the following registry keys as part of its installation routine:

HKEY_CLASSES_ROOT\CLSID\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}

HKEY_LOCAL_MACHINE\SOFTWARE\Rapport

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{6A79CF97-91F1-40BC-8CAB-44184B496B6D}

Dropping Routine

This Trojan drops the following files:

  • %System%\tftb71.dll

(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.)

Other Details

This Trojan drops the following file(s)/component(s):

  • %System%\giw

(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.)

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

7.120.10

FIRST VSAPI PATTERN DATE:

23 Apr 2010

VSAPI OPR PATTERN File:

7.121.00

VSAPI OPR PATTERN Date:

23 Apr 2010

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

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CLASSES_ROOT\CLSID
    • {6A79CF97-91F1-40BC-8CAB-44184B496B6D}
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • Rapport
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
    • {6A79CF97-91F1-40BC-8CAB-44184B496B6D}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • {6A79CF97-91F1-40BC-8CAB-44184B496B6D}

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_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Enable Browser Extensions = "yes

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_AMBLER.WJ. 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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