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TROJ_DLOADER.DBF

October 09, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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 executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

08 Mar 2008

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 Root%\Arquivos de programas\Microsoft Office\Office\bots\msg\pxador.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It executes then deletes itself afterward.

It injects threads into the following normal process(es):

  • SVCHOST.EXE

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
pxador.exe = "%System Root%\Arquivos de programas\Microsoft Office\Office\bots\msg\pxador.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
spoolsvc.exe = "%System Root%\Arquivos de programas\Microsoft Office\Office\bots\msg\spoolsvc.exe"

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}s.{BLOCKED}g.com/winup.jpg - detected as TROJ_DELF.AHU
  • http://{BLOCKED}s.{BLOCKED}g.com/Outlooks.jpg - detected as BKDR_DELF.AHZ
  • http://{BLOCKED}5.{BLOCKED}9.226.104/ftp/g.php - inaccessible

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

5.146.16

FIRST VSAPI PATTERN DATE:

08 Mar 2008

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/grayware files dropped/downloaded by TROJ_DLOADER.DBF

    • TROJ_DELF.AHU
    • BKDR_DELF.AHZ

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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\Run
    • pxador.exe = %System Root%\Arquivos de programas\Microsoft Office\Office\bots\msg\pxador.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • spoolsvc.exe = %System Root%\Arquivos de programas\Microsoft Office\Office\bots\msg\spoolsvc.exe

Step 5

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