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BKDR_POISON.BSS

June 11, 2013
 Analysis by: Adrian Cofreros
 ALIASES:

BDoor.DKI!tr.bdr(Fortinet),Backdoor.Trojan(Norton),Trojan.Win32.Generic!BT(Sunbelt)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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

  TECHNICAL DETAILS

File Size:

90,112 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Jun 2012

Arrival Details

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

  • "%Windows%\msconketfil.exe"

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random}
StubPath = "%Windows%\msconketfil.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\DefaultIcon

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\open

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\open\
command

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\open\
ddeexec

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\print

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\print\
command

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\print\
ddeexec

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\printto

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\printto\
command

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\printto\
ddeexec

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
20130401

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
20130401\Recent File List

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
20130401\Settings

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document
Default = "My2013 Document"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\DefaultIcon
Default = "{malware path}\{malware file name},1"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\open\
command
Default = "{malware path}\{malware file name} /dde"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\open\
ddeexec
Default = "[open("%1")]"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\print\
command
Default = "{malware path}\{malware file name} /dde"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\print\
ddeexec
Default = "[print("%1")]"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\printto\
command
Default = "{malware path}\{malware file name} /dde"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
My20130401.Document\shell\printto\
ddeexec
Default = "[printto("%1","%2","%3","%4")]"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}k.{BLOCKED}um.com

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.962.04

FIRST VSAPI PATTERN DATE:

05 Jun 2013

VSAPI OPR PATTERN File:

9.963.00

VSAPI OPR PATTERN Date:

06 Jun 2013

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

Identify and terminate files detected as BKDR_POISON.BSS

[ 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 3

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • My20130401.Document
  • In HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications
    • 20130401

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\Active Setup\Installed Components\{random}
    • StubPath = "%Windows%\msconketfil.exe"

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_POISON.BSS. 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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