TROJ_DELF.CNV

Malware type: Trojan

Aliases: Trojan-Downloader.Win32.Delf.ecu (Kaspersky), Downloader (Symantec), TR/Dldr.Delf.ecu (Avira), Mal/Generic-A (Sophos),

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

Medium

Distribution potential:

Low

Description: 

This Trojan may be downloaded from the Internet. It may also be dropped by another malware.

It terminates processes. It also downloads possibly malicious files from certain Web sites. However, as of this writing, the said Web sites are inaccesible.

For additional information about this threat, see:

Description created: Aug. 30, 2006 5:39:15 PM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 31,744 Bytes (.EXE file); 15,872 Bytes (.DLL file)

Initial samples received on: Aug 30, 2006

Payload 1: Downloads files

Payload 2: Terminates processes

Details:

Installation and Autostart Technique

This Trojan may be downloaded from the Internet. It may also be dropped by another malware.

Upon execution, it drops a copy of itself as REALPLAYER.EXE in the Windows system folder. It also drops its DLL component BRLMON.DLL, also detected as TROJ_DELF.CNV, in the same folder.

It creates the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Realplayer.exe = "%System%\Realplayer.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Realplayer.exe = "%System%\Realplayer.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.)

On Windows NT-based (Windows NT, 2000, XP, and Server 2003) systems, it modifies the following registry entry as part of its autostart technique:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe %System%\Realplayer.exe"

(Note: The default value for the said entry is Shell = "Explorer.exe".)

Process Termination

This Trojan terminates the following processes, most of which are related to security applications:

  • DLLShow.exe
  • DosTools.exe
  • fint2005.exe
  • HijackThis.exe
  • Killbox.exe
  • RogueCleaner.exe
  • uihost.exe
  • Unlocker.exe
  • unlockerassistant.exe

Other Details

This Trojan downloads possibly malicious files from the following Web sites:

  • http://{BLOCKED}wn.Virussky.com
  • http://www.{BLOCKED}39.com

However, as of this writing, the said Web sites are inaccesible.

Ir runs on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Alejandro Manalo

Revision History:

First pattern file version: 4.978.14
First pattern file release date: Feb 05, 2008

SOLUTION


Minimum scan engine version needed: 7.500

Pattern file needed: 5.235.00

Pattern release date: Apr 23, 2008


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Restarting in Safe Mode

This malware has characteristics that require the computer to be restarted in safe mode. Go to this page for instructions on how to restart your computer in safe mode.

Removing Autostart Entries from the Registry

Removing autostart entries from the registry prevents the malware from executing at startup.

If the registry entries below are not found, the malware may not have executed as of detection. If so, proceed to the succeeding solution set.

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate and delete the entry:
    Realplayer.exe = "%System%\Realplayer.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, and C:\Windows\System32 on Windows XP and Server 2003.)
  4. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows>CurrentVersion>Run
  5. In the right panel, locate and delete the entry:
    Realplayer.exe = "%System%\Realplayer.exe"
  6. Close Registry Editor.

Restoring Modified Entry from the Registry on Windows NT, 2000, XP, and Server 2003

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows NT>CurrentVersion>Winlogon
  3. In the right panel, locate the entry:
    Shell = "Explorer.exe %System%\Realplayer.exe"
  4. Right-click on the said entry and choose Modify. Change the value to:
    Shell = "Explorer.exe"
  5. Close Registry Editor.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Running Trend Micro Antivirus

If you are currently running in safe mode, please restart your computer normally before performing the following solution.

Scan your computer with Trend Micro antivirus and delete files detected as TROJ_DELF.CNV. To do this, Trend Micro customers must download the latest virus pattern file and scan their computer. Other Internet users can use HouseCall, the Trend Micro online virus scanner.




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