BKDR_BAYROB.KGO

 Analysis by: RonJay Kristoffer Caragay

 ALIASES:

Troj/Nivdort-CZ (Sophos); W32/Nivdort.F.gen!Eldorado (generic, not disinfectable) (F-Prot); a variant of Win32/Bayrob.AQ trojan (ESET-NOD32)

 PLATFORM:

Windows

 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:

348,160 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Dec 2015

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 copies of itself into the affected system:

  • %System Root%\qilvxhw\xxozg2yl5lmdwhmucpv.exe
  • %System Root%\qilvxhw\pekywho.exe
  • %System Root%\qilvxhw\ryfjdgz.exe

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

It drops the following files:

  • %Windows%\qilvxhw\civsyziiwm
  • %System Root%\qilvxhw\vpncktyz
  • %System Root%\qilvxhw\civsyziiwm
  • %System Root%\qilvxhw\egdpmuo

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

It creates the following folders:

  • %System Root%\qilvxhw
  • %Windows%\qilvxhw

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

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Diagnostic Encrypting Sharing Link-Layer
Start = 2

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Diagnostic Encrypting Sharing Link-Layer
ImagePath = "%System Root%\qilvxhw\pekywho.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Diagnostic Encrypting Sharing Link-Layer
DisplayName = "Diagnostic Encrypting Sharing Link-Layer"

It adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Process Proxy Name Base Level = "%System Root%\qilvxhw\pekywho.exe"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{random domain}/index.php

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.230.03

FIRST VSAPI PATTERN DATE:

24 Dec 2015

VSAPI OPR PATTERN File:

12.231.00

VSAPI OPR PATTERN Date:

25 Dec 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

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Process Proxy Name Base Level = "%System Root%\qilvxhw\pekywho.exe"

Step 5

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\SYSTEM\CurrentControlSet\Services
    • Diagnostic Encrypting Sharing Link-Layer

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.
  • %System Root%\qilvxhw
  • %Windows%\qilvxhw

Step 7

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