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BKDR_DELF.MRL

October 09, 2012
 Analysis by: Cris Nowell Pantanilla
 ALIASES:

[MICROSOFT] PWS:Win32/OnLineGames.LV,[KASPERSKY] Trojan-Downloader.Win32.Delf.hlsz

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


This backdoor may arrive bundled with malware packages as a malware component. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be dropped by other malware.

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

36,864 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

02 Mar 2012

Arrival Details

This backdoor may arrive bundled with malware packages as a malware component.

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It may be dropped by the following malware:

  • TROJ_DROPPR.MRL

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
{malware name} = "rundll32.exe %User Temp%\{malware name}.dll,XMLResCfun {malware name} 0"

Backdoor Routine

This backdoor connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}me.com:443

However, as of this writing, the said sites are inaccessible.

NOTES:

This backdoor is capable of the following commands:

  • Create Process
  • List Files
  • List Running Processes
  • Open/Read File
  • Wait for Command

  SOLUTION

Minimum Scan Engine:

9.200

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 the malware/grayware file that dropped/downloaded BKDR_DELF.MRL

    TROJ_DROPPR.MRL

Step 3

Scan your computer with your Trend Micro product and note files detected as BKDR_DELF.MRL

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete the registry entry with an unknown data 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
    • {malware name} = "rundll32.exe *User Temp%\{malware name}.dll,XMLResCfun {malware name} 0"

Step 6

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