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Backdoor.Win32.MUDDY.AA

November 08, 2018
 Analysis by: Noel Anthony Llimos
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 SYSTEM IMPACT RATING:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

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

  TECHNICAL DETAILS

File Size:

16,959 bytes

File Type:

Other

Memory Resident:

Yes

Initial Samples Received Date:

30 Oct 2018

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_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Hex Values} = %System%\rundll32.exe advpack.dll,LaunchINFSection %Temp%\Service.html,Excel,1

Backdoor Routine

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

  • Download and Execute Files

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

  • http://78.1{BLOCKED}9.148
  • http://79.1{BLOCKED}4.203
  • http://104.2{BLOCKED}3.17
  • http://185.3{BLOCKED}6.82

Information Theft

This Backdoor gathers the following data:

  • OS Version
  • OS Architecture
  • Computer System Domain
  • Computer Name
  • Username
  • IP Address
  • Checks if the current user have Administrative Rights

Other Details

This Backdoor connects to the following URL(s) to get the affected system's IP address:

  • http://ipv4bot.whatismyipadd

It does the following:

  • This malware does not run on its own and for it to run properly, it requires to be executed via powershell with specific arguments and procedures.

It adds the following scheduled tasks:

  • Task Name: WindowsDefenderUpdaterNT
  • Task Action: %Temp%\Service.html,Excel,1
  • Task Trigger: Every System Startup

(Note: %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.602.03

FIRST VSAPI PATTERN DATE:

02 Nov 2018

VSAPI OPR PATTERN File:

14.603.00

VSAPI OPR PATTERN Date:

03 Nov 2018

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\Run
    • {Hex Values} = %System%\rundll32.exe advpack.dll,LaunchINFSection %Temp%\Service.html,Excel,1

Step 5

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

  • WindowsDefenderUpdaterNT - %Temp%\Service.html,Excel,1

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.MUDDY.AA. 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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