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BKDR_MOSUCKER.AD

July 25, 2013
 ALIASES:

Backdoor:Win32/Mosucker.gen (Microsoft); Backdoor.Mosuck (Symantec); Backdoor.Win32.MoSucker.ee (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse BackDoor.SmallX.MM (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

817,128 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 May 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.

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\Run
lsass = "%Windows%\Fonts\lsass.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
lsass = "%Windows%\Fonts\lsass.exe /RunOnce"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnceEx
lsass = "%Windows%\Fonts\lsass.exe"

Other System Modifications

This backdoor deletes the following files:

  • %System%\drivers\etc\hosts

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
Options\Windows XP

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF

It adds the following registry entries:

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
Options\Windows XP
1 = "????®?{@}{@}"

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF
# = "???¨?v??¬Î²¼¨¾Îƾ¿Å½Á »Ê´?Ë~¼Á³"

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF
1 = "?£??¡vU??x?t??sY?????uo§ "

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF
2 = "£?¨?v??¬?~v??S???v???T????w???a??~?y??S?"

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
Options\Windows XP
1 = "¡ ¡{@}{@}"

Dropping Routine

This backdoor drops the following files:

  • %System Root%\wqzupw.bat

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://www.{BLOCKED}ad-area51.com/a.set

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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\VB and VBA Program Settings\Options
    • Windows XP
  • In HKEY_CURRENT_USER\Software\VB and VBA Program Settings
    • KZPXLHVLK58059210000LLGQF

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\Run
    • lsass = "%Windows%\Fonts\lsass.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
    • lsass = "%Windows%\Fonts\lsass.exe /RunOnce"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx
    • lsass = "%Windows%\Fonts\lsass.exe"
  • In HKEY_CURRENT_USER\Software\VB and VBA Program Settings\Options\Windows XP
    • 1 = "????®?{@}{@}"
  • In HKEY_CURRENT_USER\Software\VB and VBA Program Settings\KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF
    • # = "???¨?v??¬Î²¼¨¾Îƾ¿Å½Á »Ê´?Ë~¼Á³"
  • In HKEY_CURRENT_USER\Software\VB and VBA Program Settings\KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF
    • 1 = "?£??¡vU??x?t??sY?????uo§ "
  • In HKEY_CURRENT_USER\Software\VB and VBA Program Settings\KZPXLHVLK58059210000LLGQF\KZPXLHVLK58059210000LLGQF
    • 2 = "£?¨?v??¬?~v??S???v???T????w???a??~?y??S?"
  • In HKEY_CURRENT_USER\Software\VB and VBA Program Settings\Options\Windows XP
    • 1 = "¡ ¡{@}{@}"

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.
  • %System Root%\wqzupw.bat

Step 6

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

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %System%\drivers\etc\hosts


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