BKDR_NUCLEAR.BO

November 26, 2012
 ALIASES:

TrojanDownloader:Win32/Small.gen!I (Microsoft); [000082e8.EXE]:BackDoor-CQN (McAfee); Backdoor.Trojan (Symantec); Backdoor.Win32.Nuclear.ag (Kaspersky); BehavesLike.Win32.Malware.eah (mx-v) (Sunbelt); Backdoor.Generic.78251 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor 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:

217,600 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 Nov 2012

Arrival Details

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

  • %Windows%\NR\MSNddfe3.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It creates the following folders:

  • %Windows%\NR

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MSNddfe3 = "%Windows%\NR\MSNddfe3.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MSNddfe3 = "%Windows%\NR\MSNddfe3.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{411EDCF7-755D-414E-A74B-3DBB65570589}
StubPath = "%Windows%\NR\MSNddfe3.exe opt"

Other System Modifications

This backdoor deletes the following files:

  • %Windows%\NR\MSNddfe3.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It adds the following registry keys:

HKEY_CLASSES_ROOT\dllfile\shell\
open\command

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{411EDCF7-755D-414E-A74B-3DBB65570589}

Dropping Routine

This backdoor drops the following files:

  • %Windows%\NR\MSN4dsrt4w.dll
  • %User Temp%\_ssf.vbs

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

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

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_CLASSES_ROOT\dllfile\shell\open
    • command
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {411EDCF7-755D-414E-A74B-3DBB65570589}

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\Windows\CurrentVersion\Run
    • MSNddfe3 = "%Windows%\NR\MSNddfe3.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MSNddfe3 = "%Windows%\NR\MSNddfe3.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{411EDCF7-755D-414E-A74B-3DBB65570589}
    • StubPath = "%Windows%\NR\MSNddfe3.exe opt"

Step 5

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.
  • %Windows%\NR\MSN4dsrt4w.dll
  • %User Temp%\_ssf.vbs

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Windows%\NR

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_NUCLEAR.BO. 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.

  • %Windows%\NR\MSNddfe3.exe


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