Analysis by: kathleenno
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This backdoor may be dropped by TROJ_MDROP.EV.

It executes commands from a remote malicious user to delete, download, execute or upload files, get system information and kill processes.

It connects to servers using TCP port 6386.

It executes commands from a remote malicious user, effectively compromising the affected system.

This backdoor may be dropped by other malware.

  TECHNICAL DETAILS

Ports: TCP port 6386 (Unassigned)
File Size: 35,328 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 16 Mar 2011
Payload: Compromises system security

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_MDROP.EV

Installation

This backdoor drops the following files:

  • %System%\csrls.dll - also detected as BKDR_LAPUK.D

(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 drops the following copies of itself into the affected system:

  • %System%\{malware file name}.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 processes:

  • %Program Files%\Internet Explorer\IEXPLORE.EXE
  • %System%\services.exe
  • %System%\lsass.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.. %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 backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
Athene = "{malware path and file name}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
Athene = "{malware path and file name}"

NOTES:

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • delete file
  • download file
  • execute file
  • get system information
  • kill process
  • upload file

Other Details

This backdoor does the following:

Connects to any of the following servers using TCP port 6386:

  • {BLOCKED}4.{BLOCKED}3.215.70
  • {BLOCKED}5.5.227.69

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 7.910.04
FIRST VSAPI PATTERN DATE: 17 Mar 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 BKDR_LAPUK.D

Step 3

Scan your computer with your Trend Micro product and note files detected as BKDR_LAPUK.D

Step 4

Restart in Safe Mode

[ Learn More ]

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\Windows\CurrentVersion\policies\Explorer\Run
    • Athene = "{malware path and file name}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
    • Athene = "{malware path and file name}"

Step 6

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