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TROJ_KREPPER.AI

October 09, 2012
 ALIASES:

BrowserModifier:Win32/Melkosoft, TrojanDownloader:Win32/Small.ABP, BrowserModifier:Win32/Melkosoft, (Microsoft); [00016e00.EXE\000012b0.EXE]:AdClicker-AF.dr, [00006000.EXE]:AdClicker-AF.dll (McAfee); Trojan.SuperSpider (Symantec); Trojan.Win32.Krepper.ae (Kaspersky); BehavesLike.Win32.Malware.ssc (mx-v) (Sunbelt)

 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

File Size:

214,016 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

09 Oct 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.

Installation

This Trojan drops the following copies of itself into the affected system:

  • %System%\2rs3cesit51thd.exe

(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 System Modifications

This Trojan adds the following registry keys:

HKEY_CLASSES_ROOT\Plugin6.DNSErrObj.1

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Plugin6.DNSErrObj.1\CLSID

HKEY_CLASSES_ROOT\Plugin6.DNSErrObj

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Plugin6.DNSErrObj\CLSID

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Plugin6.DNSErrObj\CurVer

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\ProgID

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\VersionIndependentProgID

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\Programmable

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\InprocServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\TypeLib

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0\
FLAGS

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0\
0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0\
0\win32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0\
HELPDIR

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}\ProxyStubClsid

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}\ProxyStubClsid32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}\TypeLib

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\InprocServer32
ThreadingModel = "Apartment"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}\TypeLib
Version = "1.0"

Dropping Routine

This Trojan drops the following files:

  • %System%\nt3x66snef5ru.dll
  • %System%\9hhnmwlpg96.dll
  • %System%\nhdwxpidtvkjkmt.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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

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
    • Plugin6.DNSErrObj.1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Plugin6.DNSErrObj.1
    • CLSID
  • In HKEY_CLASSES_ROOT
    • Plugin6.DNSErrObj
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Plugin6.DNSErrObj
    • CLSID
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Plugin6.DNSErrObj
    • CurVer
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
    • {467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}
    • ProgID
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}
    • VersionIndependentProgID
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}
    • Programmable
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}
    • InprocServer32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}
    • TypeLib
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib
    • {444A5674-FF85-45D4-9AE2-4199D8D70C85}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}
    • 1.0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0
    • FLAGS
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0
    • 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0\0
    • win32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{444A5674-FF85-45D4-9AE2-4199D8D70C85}\1.0
    • HELPDIR
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
    • {0D721150-AEF3-457B-B03A-5097B623CE45}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}
    • ProxyStubClsid
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}
    • ProxyStubClsid32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}
    • TypeLib

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_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{467FAEB2-5F5B-4c81-BAE0-2A4752CA7F4E}\InprocServer32
    • ThreadingModel = "Apartment"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{0D721150-AEF3-457B-B03A-5097B623CE45}\TypeLib
    • Version = "1.0"

Step 4

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.
  • %System%\nt3x66snef5ru.dll
  • %System%\9hhnmwlpg96.dll
  • %System%\nhdwxpidtvkjkmt.dll

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_KREPPER.AI. 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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