Analysis by: Cris Nowell Pantanilla
 Modified by: Christopher Daniel So
ALIASES:

Trojan:Win32/Lukicsel.I (Microsoft), Backdoor.Trojan (Symantec), Generic Backdoor.us (McAfee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

This Trojan may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 50,688 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 01 Nov 2011
Payload: Drops files

Arrival Details

This Trojan may be dropped by other malware.

Installation

This Trojan drops the following non-malicious file:

  • %System%\crt.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.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
DllName = "mdhcp32.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Startup = "WinStart2EX"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Logoff = "WinOff2EX"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Shutdown = "WinOff2EX"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Asynchronous = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Impersonate = "0"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32

Dropping Routine

This Trojan drops the following files:

  • %System%\dll.dll - detected by Trend Micro as TROJ_LUKICSEL.AE

(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.)

NOTES:

This Trojan forces all threads of all running SVCHOST.EXE processes to load the dropped component %System%\dll.dll.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.540.05
FIRST VSAPI PATTERN DATE: 01 Nov 2011
VSAPI OPR PATTERN File: 8.541.00
VSAPI OPR PATTERN Date: 02 Nov 2011

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

Remove malware files dropped/downloaded by TROJ_LUKICSEL.AC

    • TROJ_LUKICSEL.AE

Step 3

Restart in Safe Mode

[ Learn More ]

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.

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
  • mdhcp32

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%\crt.dat

Step 6

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