Analysis by: Jimelle Monteser
ALIASES:

Trojan-Dropper.Win32.Dapato (Ikarus), Trojan-Dropper.Win32.Dapato.bcgo (Kaspersky), Backdoor:MSIL/Pontoeb.N (Microsoft)

 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: 49,152 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Jun 2013

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:

  • %All Users Profile%\wscntfy.exe
  • %Program Files%\Common Files\lsmass.exe

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

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\policies\
Explorer\Run
Windows-Network Component = "%Program Files%\Common Files\lsmass.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows-Audio Driver = "%All Users Profile%\wscntfy.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{e2d01591-c92b-11df-94c2-806d6172696f}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
EnableBalloonTips = "0"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLUA = "0"

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%All Users Profile%\wscntfy.exe = "%All Users Profile%\wscntfy.exe:*:Enabled:Windows-Audio Driver"

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%All Users Profile%\wscntfy.exe = "%All Users Profile%\wscntfy.exe:*:Enabled:Windows-Audio Driver"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://q.{BLOCKED}a.ru/gate.php

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.972.03
FIRST VSAPI PATTERN DATE: 10 Jun 2013
VSAPI OPR PATTERN File: 9.973.00
VSAPI OPR PATTERN Date: 11 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

Restart in Safe Mode

[ Learn More ]

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.

 
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Active Setup\Installed Components
    • {e2d01591-c92b-11df-94c2-806d6172696f}

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\policies\Explorer\Run
    • Windows-Network Component = "%Program Files%\Common Files\lsmass.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows-Audio Driver = "%All Users Profile%\wscntfy.exe"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • Hidden = "2"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • EnableBalloonTips = "0"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\system
    • EnableLUA = "0"
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %All Users Profile%\wscntfy.exe = "%All Users Profile%\wscntfy.exe:*:Enabled:Windows-Audio Driver"
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %All Users Profile%\wscntfy.exe = "%All Users Profile%\wscntfy.exe:*:Enabled:Windows-Audio Driver"

Step 5

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