TROJ_DELF.BN


 ALIASES:

TrojanDropper:Win32/Delf.BN, VirTool:Win32/DelfInject.gen!AH (Microsoft); BackDoor-AMQ (McAfee); Backdoor.Beasty.dr (Symantec); Trojan-Dropper.Win32.Small.amw (Kaspersky); RiskTool.Win32.ProcessPatcher.Nor!cobra (v) (not malicious) (Sunbelt); MemScan:Backdoor.Darkmoon.52 (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 disables Task Manager, Registry Editor, and Folder Options.

  TECHNICAL DETAILS

File Size:

552,862 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Nov 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\{42CE4021-DE03-E3CC-EA32-40BB12E6015D}
StubPath = "%System%\mskndn.com"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SAM\A

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{42CE4021-DE03-E3CC-EA32-40BB12E6015D}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

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

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Check_Associations = "No"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
COM Service = "%Windows%\msagent\msvsui.com"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess
Start = "4"

(Note: The default value data of the said registry entry is 2.)

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
COM Service = "%Windows%\msagent\msvsui.com"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\patriotas1.exe
  • %User Temp%\Cartas Magicas.exe
  • server.exe
  • osum.exe
  • %User Temp%\Cartas Magicas.exe_
  • %Windows%\msagent
  • %Windows%\svchost.exe
  • %System%\mskndn.com
  • %Windows%\msagent\msvsui.com

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

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.

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_LOCAL_MACHINE\SAM
    • A
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {42CE4021-DE03-E3CC-EA32-40BB12E6015D}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run

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\Microsoft\Active Setup\Installed Components\{42CE4021-DE03-E3CC-EA32-40BB12E6015D}
    • StubPath = "%System%\mskndn.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Check_Associations = "No"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • COM Service = "%Windows%\msagent\msvsui.com"

Step 6

Restore this modified 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\SYSTEM\ControlSet001\Services\SharedAccess
    • From: Start = "4"
      To: Start = ""2""

Step 7

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.
  • %User Temp%\patriotas1.exe
  • %User Temp%\Cartas Magicas.exe
  • server.exe
  • osum.exe
  • %User Temp%\Cartas Magicas.exe_
  • %Windows%\msagent
  • %Windows%\svchost.exe
  • %System%\mskndn.com
  • %Windows%\msagent\msvsui.com

Step 8

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