BKDR_DEXTR.C

 Analysis by: Mark Joseph Manahan

 ALIASES:

PWS:Win32/Dexter.A (Microsoft), RDN/Generic PWS.y!vc (McAfee), a variant of Win32/Poxters.A trojan (Eset)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet

This backdoor may be unknowingly downloaded by a user while visiting malicious websites.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It logs a user's keystrokes to steal information.

  TECHNICAL DETAILS

File Size:

40,448 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Dec 2013

Payload:

Collects system information, Compromises system security, Steals information

Arrival Details

This backdoor may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This backdoor drops the following file(s)/component(s):

  • {Malware Path}\SecureDll.dll - keylogger module loaded to iexplore.exe also detected as BKDR_DEXTR.C

It drops the following copies of itself into the affected system:

  • %Application Data%\Java Security Plugin\javaplugin.exe

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

It adds the following processes:

  • iexplore.exe

It creates the following folders:

  • %Application Data%\Java Security Plugin

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

It injects itself into the following processes as part of its memory residency routine:

  • iexplore.exe created process

Autostart Technique

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

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Sun Java Security Plugin = "%Application Data%\Java Security Plugin\javaplugin.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Sun Java Security Plugin = "%Application Data%\Java Security Plugin\javaplugin.exe"

It drops the following files:

  • {malware path}\strokes.log
  • {malware path\tmp.log
  • {malware path}\debug.log

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\HelperSolutions Software

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Associations

It adds the following registry entries:

HKEY_CURRENT_USER\Software\HelperSolutions Software
digit = "{GUID}"

HKEY_CURRENT_USER\Software\HelperSolutions Software
val1 = "{malware path}\strokes.log"

HKEY_CURRENT_USER\Software\HelperSolutions Software
val2 = "{malware path}\tmp.log"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Associations
LowRiskFileTypes = ".exe;.bat;.reg;.vbs;"

Backdoor Routine

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

  • Update (update copy)
  • Checkin (set the delay it sends information)
  • Scanin (set the delay it checks memory for information)
  • Uninstall (uninstall itself)
  • Download (download and execute a file)

It connects to the following websites to send and receive information:

  • hi.{BLOCKED}o.biz/fk/gateway.php
  • {BLOCKED}.{BLOCKED}.115.107/ial9121988921973dsadas8dsa080dsa/gateway.php
  • {BLOCKED}.{BLOCKED}.44.11/base1/gateway.php
  • {BLOCKED}.{BLOCKED}.44.11/w19218317418621031041543/gateway.php
  • {BLOCKED}-service.in.ua/alfa/gateway.php
  • {BLOCKED}.{BLOCKED}.67.242/~microsre/9e6e2103559968f8a876156c6ff2acad/gateway.php
  • {BLOCKED}.{BLOCKED}.78.24/e78826c4e629f7036312259d7a83ed05/gateway.php

Information Theft

This backdoor gathers the following data:

  • {GUID}
  • Username
  • Hostname
  • Operating System
  • Processor type
  • List of running processes
  • Key to decrypt sent information

It logs a user's keystrokes to steal information.

NOTES:

It dumps the affected system's memory to check for sensitive information, such as payment details and/or credit card information stored in the aforementioned system.

  SOLUTION

Minimum Scan Engine:

9.700

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_CURRENT_USER\Software
    • HelperSolutions Software
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
    • Associations

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_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Sun Java Security Plugin = "%Application Data%\Java Security Plugin\javaplugin.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Sun Java Security Plugin = "%Application Data%\Java Security Plugin\javaplugin.exe"

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Application Data%\Java Security Plugin

Step 6

Search and delete these files

[ Learn More ]
There may be some component 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.
  • {malware path}\strokes.log
  • {malware path\tmp.log
  • {malware path}\debug.log

Step 7

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