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Threat Encyclopedia

BKDR_DLDR.A

ANALYSIS BY

Abraham Latimer Camba


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

Infection Channel:

Dropped by other malware


This backdoor arrives as a dropped malware. It is an Enfal/Lurid malware that has been used in other targeted attacks in the past. This backdoor's dropper, TROJ_ARTIEF.SDY, comes as a .DOC file attachment to spammed email about the Hurricane Sandy devastation.

To get a one-glance comprehensive view of the behavior of this Backdoor, refer to the Threat Diagram shown below.

For the related story, you may read the blog post NATO's NSHQ Targeted by Attack Leveraging Hurricane Sandy

This backdoor may be dropped by other malware.

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

TECHNICAL DETAILS

File Size:

32,768 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

16 Nov 2012

Payload:

Connects to URLs/IPs, Compromises system security

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_ARTIEF.SDY

Installation

This backdoor drops the following copies of itself into the affected system and executes them:

  • %User Temp%\adobeupd.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • HTTPS-GNIK
  • MAINHTTPS
  • RMTCURR

Autostart Technique

This backdoor drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\Adobe Center.lnk
  • All Users' %User Startup%\Adobe Center.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Backdoor Routine

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

  • Download files from C&C server
  • Upload files to C&C server
  • Enumerate drives
  • Get drive information
  • Enumerate files/folders
  • Find files/folders
  • Get file information
  • Create files/folders
  • Modify files/folders
  • Copy files/folders
  • Delete files/folders
  • Execute files
  • Terminate processes
  • Get time zone information
  • Perform remote shell
  • Sleep for a specified amount of time

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

  • https://domain.{BLOCKED}2.us

It posts the following information to its command and control (C&C) server:

  • Host name
  • MAC address
  • OS version information

SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.530.03

FIRST VSAPI PATTERN DATE:

16 Nov 2012

VSAPI OPR PATTERN File:

9.531.00

VSAPI OPR PATTERN Date:

17 Nov 2012

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Remove the malware/grayware file that dropped/downloaded BKDR_DLDR.A

Step 3

Identify and terminate files detected as BKDR_DLDR.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Search and delete this file

[ Learn More ]
There may be some 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.
  • %User Startup%\Adobe Center.lnk
  • All Users' %User Startup%\Adobe Center.lnk

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_DLDR.A. 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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