BKDR_SHOTODOR.UJ

August 18, 2014
 Modified by: RonJay Kristoffer Caragay
 ALIASES:

W32/AutoIt-AMK, Troj/Malit-EX (Sophos); DR/AutoIt.Gen (AntiVir); RAR/Agent.AO trojan (NOD32)

 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:

  • 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:

1,635,258 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

18 Aug 2014

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 Profile%\28wen8zu1\AUigfNtXMnK.UZY
  • %User Profile%\28wen8zu1\bfblpixs.vbs
  • %User Profile%\28wen8zu1\blTtgYEoj.exe
  • %User Profile%\28wen8zu1\eqqcnrdavmwga.cmd
  • %User Profile%\28wen8zu1\joWvKCjDXqU.TNX
  • %User Profile%\28wen8zu1\rHdDYwWqx.KRY
  • %User Profile%\28wen8zu1\run.vbs
  • %User Startup%\RegSvcs.exe

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

It creates the following folders:

  • %User Profile%\28wen8zu1

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

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\RunOnce
28wen8zu1 = "%User Profile%\28wen8zu1\bfblpixs.vbs"

Other Details

This backdoor connects to the following possibly malicious URL:

  • smtp.{BLOCKED}aders.com
  • http://www.myip.ru/en-EN/index.php

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.958.02

FIRST VSAPI PATTERN DATE:

01 Aug 2014

VSAPI OPR PATTERN File:

10.959.00

VSAPI OPR PATTERN Date:

01 Aug 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

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\RunOnce
    • 28wen8zu1 = "%User Profile%\28wen8zu1\bfblpixs.vbs"

Step 5

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 Profile%\28wen8zu1\AUigfNtXMnK.UZY
  • %User Profile%\28wen8zu1\bfblpixs.vbs
  • %User Profile%\28wen8zu1\blTtgYEoj.exe
  • %User Profile%\28wen8zu1\eqqcnrdavmwga.cmd
  • %User Profile%\28wen8zu1\joWvKCjDXqU.TNX
  • %User Profile%\28wen8zu1\rHdDYwWqx.KRY
  • %User Profile%\28wen8zu1\run.vbs
  • %User Startup%\RegSvcs.exe

Step 6

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.
  • %User Profile%\28wen8zu1

Step 7

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