TROJ_OBFUSC.BZ

October 12, 2012
 ALIASES:

Gen:Trojan.Heur.PT.iiZabKBkEOh (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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

140,279 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{11CDF7EC-651B-76AA-AD69-4005FE080DE8}
stubpath = "%System%\sgfcntf.exe s"

Other System Modifications

This Trojan deletes the following files:

  • %System%\sgfcntf.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.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{11CDF7EC-651B-76AA-AD69-4005FE080DE8}

HKEY_LOCAL_MACHINE\SOFTWARE\NKav

HKEY_CURRENT_USER\SOFTWARE\NKav

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\MediaResources\msvideo

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\NKav
nck = "{random values}"

HKEY_CURRENT_USER\Software\NKav
klg = "{random values}"

HKEY_CURRENT_USER\Software\NKav
plg1 = "{random values}"

Dropping Routine

This Trojan drops the following files:

  • %System%\sgfcntf.dat

(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 deletes itself after execution.

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

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\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {11CDF7EC-651B-76AA-AD69-4005FE080DE8}
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • NKav
  • In HKEY_CURRENT_USER\SOFTWARE
    • NKav
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MediaResources
    • msvideo

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\Active Setup\Installed Components\{11CDF7EC-651B-76AA-AD69-4005FE080DE8}
    • stubpath = "%System%\sgfcntf.exe s"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\NKav
    • nck = "{random values}"
  • In HKEY_CURRENT_USER\Software\NKav
    • klg = "{random values}"
  • In HKEY_CURRENT_USER\Software\NKav
    • plg1 = "{random values}"

Step 5

Search and delete this file

[ 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%\sgfcntf.dat

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_OBFUSC.BZ. 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 7

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.

  • %System%\sgfcntf.exe


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