ALIASES:

Backdoor:Win32/Fynloski.A (Microsoft); Generic Dropper.ay (McAfee); Packed.Win32.Krap.es (Kaspersky); Trojan-Dropper.Win32.Delf.anx (v) (Sunbelt); Rogue:W32/FakeAv.BI (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: 862,720 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 13 Jan 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%\MSDCSC\msdcsc.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It creates the following folders:

  • %System%\MSDCSC
  • %User Temp%\dclogs

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.. %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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
RunDll32 = "%System%\MSDCSC\msdcsc.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\DC3_FEXEC

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
UserInit = "%System%\userinit.exe,%System%\MSDCSC\msdcsc.exe"

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

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/spyware.

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_CURRENT_USER\Software
    • DC3_FEXEC
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
    • System

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • RunDll32="%System%\MSDCSC\msdcsc.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • UserInit="%System%\userinit.exe,%System%\MSDCSC\msdcsc.exe"

Step 6

Search and delete these folders

[ 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.
  • %System%\MSDCSC
  • %User Temp%\dclogs

Step 7

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