BKDR_SATHUR.A

 Analysis by: Francis Xavier Antazo

 ALIASES:

a variant of Win32/Sathurbot.L (ESET),

 PLATFORM:

Windows

 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

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 terminates itself if it detects it is being run in a virtual environment.

  TECHNICAL DETAILS

File Size:

1,830,912 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

02 May 2015

Payload:

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 component file(s):

  • {Malware Path}\SecurityHelper.dll {detected as BKDR_SATHUR.A}

It injects itself into the following processes running in the affected system's memory:

  • explorer.exe
  • rundll32.exe
  • regsvr32.exe

It creates the following folders:

  • {Malware Path}\temp
  • {Malware Path}\SecurityCache\
  • {Malware Path}\SecurityCache\cache
  • {Malware Path}\SecurityCache\data

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

  • Global\{982C49E7-2232-4B26-B379-309AFAB28096}

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{3B5B973C-92A4-4855-9D3F-0F3D23332208}\InprocServer

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\0PerformanceMonitor

It adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{3B5B973C-92A4-4855-9D3F-0F3D23332208}
(Default) = "Windows Performance Monitor"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{3B5B973C-92A4-4855-9D3F-0F3D23332208}\InprocServer32
(Default) = "%All Users Profile%\Application Data\Application Data\Microsoft\Performance\Monitor\PerformanceMonitor.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\0PerformanceMonitor
(Default) = "{3B5B973C-92A4-4855-9D3F-0F3D23332208}"

Backdoor Routine

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

  • Get system information
  • Update the copy of the trojan
  • Run arbitrary files

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

  • {BLOCKED}i8asdaskjdkn.in

Other Details

This backdoor terminates itself if it detects it is being run in a virtual environment.

NOTES:

This backdoor checks for the following as part of its anti-sandbox and anti-virtual machine routines:

  • Existence of the following windows:
    • SandboxieControlWndClass (sandboxie)
    • Afx:400000:0 (Winjail Sandbox)
  • Running process path contains:
    • sample (Anubis sandbox)
    • file.exe (sunbelt sandbox)
  • Username is:
    • andy (Anubis sandbox)
    • vmdg
    • currentuser (Norman Sandbox)
    • schmidti (CW sandbox)
  • Existence of the following VMWare-related files:
    • vmupgradehelper.exe
    • vmwareuser.exe
    • vmwaretray.exe
    • vmtoolsd.exe
    • vmtoolsd.exe
  • Existence of the following VBox related files:
    • vboxservice.exe
    • vboxtray.exe

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.778.03

FIRST VSAPI PATTERN DATE:

08 Jul 2015

VSAPI OPR PATTERN File:

11.779.00

VSAPI OPR PATTERN Date:

09 Jul 2015

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

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_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{3B5B973C-92A4-4855-9D3F-0F3D23332208}
    • InprocServer
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers
    • 0PerformanceMonitor

Step 3

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\Classes\CLSID\{3B5B973C-92A4-4855-9D3F-0F3D23332208}
    • (Default) = "Windows Performance Monitor"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{3B5B973C-92A4-4855-9D3F-0F3D23332208}\InprocServer32
    • (Default) = "%All Users Profile%\Application Data\Application Data\Microsoft\Performance\Monitor\PerformanceMonitor.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers\0PerformanceMonitor
    • (Default) = "{3B5B973C-92A4-4855-9D3F-0F3D23332208}"

Step 4

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