WORM.WIN32.KAXELA.AA

 Analysis by: Augusto II Remillano

 ALIASES:

W32/Winko.worm (NAI), GenPack:Win32.Worm.Winko.T (BitDefender)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

12,976 bytes

File Type:

EXE

File Compression:

NSPack

Memory Resident:

Yes

Initial Samples Received Date:

22 Nov 2018

Payload:

Drops files, Modifies system registry, Downloads files

Arrival Details

This Worm 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 Worm drops the following files:

  • %System%\{eight random characters}.dll -> detected as WORM_AUTORUN.TA
  • %System%\del.bat - script responsible for the deletion of initially executed copy of the malware
  • {All drives}\autorun.inf

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

It drops the following copies of itself into the affected system:

  • %System%\{eight random characters}.exe
  • {All drives}\auto.exe

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

It injects codes into the following process(es):

  • winlogon.exe
  • explorer.exe

Autostart Technique

This Worm adds and runs the following services:

  • Service Name: {eight random characters}
    Display Name: {eight random characters}
    Start Type: SERVICE_AUTO_START
    Binary Pathname: %%System%\{eight random characters}.exe

Other System Modifications

This Worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{eight random characters}
Enum =

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{eight random characters
Security =

It adds the following registry entries:

KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{eight random characters}\Enum
0 = "Root\LEGACY_{eight random characters}\0000"

KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{eight random characters}\Enum
Count = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{eight random characters}\Enum
Next Instance = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{eight random characters}\Security
Security = {value}

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PCHealth\ErrorReporting
DoReport = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PCHealth\ErrorReporting
ShowUI = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT
ReportBootOk = "1"

Propagation

The said .INF file contains the following strings:

[AutoRun]
open=auto.exe
shellexecute=auto.exe
shell\Auto\command=auto.exe

Download Routine

This Worm downloads an updated copy of itself from the following website(s):

  • http://nx.{BLOCKED}b.cn/soft//update.txt

As of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.642.06

FIRST VSAPI PATTERN DATE:

22 Nov 2018

VSAPI OPR PATTERN File:

14.643.00

VSAPI OPR PATTERN Date:

23 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

Disable this malware service

[ Learn More ]
  •  
    • {eight random characters}

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
    • {eight random characters}

Step 6

Restore these modified registry values

[ 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\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = "0"
      To: CheckedValue = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PCHealth\ErrorReporting
    • From: DoReport = "0"
      To: DoReport = "{User Preference}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PCHealth\ErrorReporting
    • From: ShowUI = "0"
      To: ShowUI = "{User Preference}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT
    • From: ReportBootOk = "1"
      To: ReportBootOk = "{User Preference}"

Step 7

Search and delete these files

[ 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%\{eight random characters}.dll
  • %System%\del.bat

Step 8

Search and delete AUTORUN.INF files created by WORM.WIN32.KAXELA.AA that contain these strings

[ Learn More ]
DATA_GENERIC
  • If the lines are present, delete the file.
  • Repeat steps 3 to 6 for the remaining AUTORUN.INF files in other remaining removable drives.
  • Close Search Results.
  • *Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).

    For Windows Vista, Windows 7, Windows Server 2003, Windows 8, Windows 8.1, and Windows Server 2012:

    1. Open a Windows Explorer window.
      • For Windows Vista, 7, and Server 2008 users, click Start>Computer.
      • For Windows 8, 8.1, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
    2. In the Search Computer/This PC input box, type:
      AUTORUN.INF
    3. Select the file, then open using Notepad.
    4. Check if the following lines are present in the file:
      DATA_GENERIC
    5. If the lines are present, delete the file.
    6. Repeat steps 3 to 5 for the remaining AUTORUN.INF files in other remaining removable drives.
    7. Close Search Results.

    Step 9

    Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM.WIN32.KAXELA.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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