BKDR_PROXY.APS

October 06, 2014
 Analysis by: Adrian Cofreros
 ALIASES:

a variant of Win32/Agent.WGN trojan, a variant of Win32/Agent.WGN trojan(NOD32),TR/Spy.205824.82(Antivir)

 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: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

206,166 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

19 Sep 2014

Payload:

Connects to URLs/IPs, Compromises system security

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 files:

  • %User Temp%\leassap.exe - detected as BKDR_PROXY.APS

(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 drops the following component file(s):

  • %User Temp%\20140805.doc

(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.)

Autostart Technique

This backdoor modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,%User Temp%\leassap.exe,"

(Note: The default value data of the said registry entry is "%System%\userinit.exe,".)

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %ProgramData%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to drop copy(Windows 7 and Vista)
  • %User Startup%\FlashUtil_ActiveX.lnk-lnk to drop copy(Windows XP)
  • %Application Data%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to drop copy(Windows 7 and Vista)
  • %All Users Profile%\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk- link to drop copy(Windows XP)

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).. %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.. %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.. %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.)

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

  • Download and execute arbitrary files
  • Use proxy server settings of current user
  • Delete Arbitrary File
  • Upload Files
  • Perform Remote Shell
  • Load a file using LoadLibrary
  • Search Files
  • Gather Proxy Settings
  • Enumerate Processes
  • Gather Credentials from the user's Credential set.(CredEnumerate)
  • Gather Credentials from Protected storage.(PStoreCreateInstance)

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

  • http://{BLOCKED}e-oowakudani.jp/book/index.php
  • http://www.{BLOCKED}i-fp.jp/book/index.php

However, as of this writing, the said sites are inaccessible.

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

  • http://www.microsoft.com
  • http://www.msftncsi.com
  • http://www.yahoo.co.jp

NOTES:

It finds the following strings on the enumerated window and then sleeps once they where seen:

  • ollydbg
  • W32Dasm
  • Wireshark
  • SoftICE
  • Process Explorer
  • Process Monitor
  • Process Hacker

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.158.05

FIRST VSAPI PATTERN DATE:

19 Sep 2014

VSAPI OPR PATTERN File:

11.159.00

VSAPI OPR PATTERN Date:

19 Sep 2014

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Restore this modified 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 NT\CurrentVersion\Winlogon
    • From: Userinit = "%System%\userinit.exe,%User Temp%\leassap.exe,"
      To: Userinit = "%System%\userinit.exe,"

Step 5

Search and delete these files

[ 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 Temp%\20140805.doc
  • %All Users Profile%\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk
  • %ProgramData%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk
  • %User Startup%\FlashUtil_ActiveX.lnk
  • %Application Data%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk

Step 6

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

Step 7

Scan your computer with your Trend Micro product to delete files detected as BKDR_PROXY.APS. 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.


Did this description help? Tell us how we did.