Backdoor.Win32.SDDOS.A


 ALIASES:

Trojan:Win32/Bulta!rfn [non_writable_container] (MICROSOFT); Backdoor.Win32.Sdbot.agiy (KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild:

  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 executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

49,664 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Jun 2020

Payload:

Drops files, Steals information, Blocks user desktop, Connects to URLs/IPs

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:

  • %Application Data%\WindowsUpdata\.temp.fortest - main malware was ran without admin privilege
  • %Windows%\WindowsUpdata\.temp.fortest - main malware was ran with admin privilege

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops and executes the following files:

  • %Application Data%\WindowsUpdata\{random}.exe - main malware was ran without admin privilege
  • %Windows%\WindowsUpdata\{random}.exe - main malware was ran with admin privilege

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It adds the following processes:

  • %System%\cmd.exe /c del {Malware path and name} > nul - delete original malware

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It creates the following folders:

  • %Application Data%\WindowsUpdata - main malware was ran without admin privilege
  • %Windows%\WindowsUpdata - main malware was ran with admin privilege

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • siukit.cn

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
{Random Malware Name}.exe = %Windows%\WindowsUpdata\{random}.exe - main malware was ran with admin privilege

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Malware Name}.exe = %Application Data%\WindowsUpdata\{Random}.exe - main malware was ran without admin privilege

Other System Modifications

This Backdoor modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UACDisableNotify = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
PromptOnSecureDesktop = 0

Backdoor Routine

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

  • Perforn DDoS Attacks on specific IP address
  • Download files

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

  • {BLOCKED}.{BLOCKED}.133.49:2553

Denial of Service (DoS) Attack

This Backdoor is capable of performing various network denial-of-service (DoS) attacks:

  • {BLOCKED}.{BLOCKED}.153.99:1024
  • {BLOCKED}.{BLOCKED}.210.236:1024

Information Theft

This Backdoor gathers the following data:

  • Windows Version
  • Current Memory Usage
  • System Hardware Information
  • Username
  • Computer name
  • IP address

Other Details

This Backdoor does the following:

  • It requires the following file in order to perform its other routines:
    • Config.ini
  • It sends the gathered information to its server.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.912.04

FIRST VSAPI PATTERN DATE:

05 Jun 2020

VSAPI OPR PATTERN File:

15.913.00

VSAPI OPR PATTERN Date:

06 Jun 2020

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     Troj.Win32.TRX.XXPE50FFF035

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Restart in Safe Mode

[ Learn More ]

Step 5

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
    • {Random Malware Name}.exe = %Application Data%\WindowsUpdata\{Random}.exe
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • {Random Malware Name}.exe = %Windows%\WindowsUpdata\{random}.exe

Step 6

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: UACDisableNotify = 0
      To: UACDisableNotify = {Default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • From: EnableLUA = 0
      To: EnableLUA = {Default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • From: PromptOnSecureDesktop = 0
      To: PromptOnSecureDesktop = {Default}

Step 7

Search and delete this folder

[ 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%\WindowsUpdata
  • %Windows%\WindowsUpdata

Step 8

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