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Worm.Win32.WUKILL.AA

December 04, 2019
 Modified by: Henry Alarcon Jr.
 ALIASES:

Worm:Win32/Wukill.AG@mm (MICROSOFT); W32/Traxg.B@mm (FORTINET);

 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:

Propagates via removable drives, Propagates via email


This Worm arrives as an attachment to email messages mass-mailed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops copies of itself in all drives. These dropped copies use the names of the folders located on the said drives for their file names. It gathers target email addresses from the Windows Address Book (WAB).

  TECHNICAL DETAILS

File Size:

16,797,696 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

27 Nov 2019

Arrival Details

This Worm arrives as an attachment to email messages mass-mailed by other malware/grayware or malicious users.

It 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 copies of itself into the affected system:

  • %Fonts%\{random}.com
  • %Windows%\Document.exe

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
TempCom = %Fonts%\{random}.com

Other System Modifications

This Worm modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "0"

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"

(Note: The default value data of the said registry entry is 0.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPath = "1"

(Note: The default value data of the said registry entry is 0.)

It also creates the following registry entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Setup
KaV300XP = "{number}"

Propagation

This Worm drops the following copies of itself in all physical and removable drives:

  • {drive letter}:\{string}
    • where {string} can be any of the following strings:
      • EXPLORER.exe
      • Explorer.EXE
      • WINDOWS.EXE
      • Windows.exe
      • Ghost.bat

It drops copies of itself in all drives. These dropped copies use the names of the folders located on the said drives for their file names.

It gathers target email addresses from the Windows Address Book (WAB).

It sends the following message(s):

Subject:{non-English characters}
Message Body: {non-English characters}
Attachment: Document.exe

Dropping Routine

This Worm drops the following files:

  • {path}\folder.htt
    Notes: Path is where it drops copies of itself and use the names of the folders where its located (i.e. D:\sample\sample.exe)

Other Details

This Worm sets the attributes of the following file(s) to Hidden and System:

  • {path}\folder.htt
    Notes: Path is where it drops copies of itself and use the names of the folders where its located (i.e. D:\sample\sample.exe)

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

15.524.06

FIRST VSAPI PATTERN DATE:

27 Nov 2019

VSAPI OPR PATTERN File:

15.525.00

VSAPI OPR PATTERN Date:

28 Nov 2019

Step 1

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 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

Identify and terminate files detected as Worm.Win32.WUKILL.AA

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • TempCom = "%Fonts%\{random}.com"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup
    • KaV300XP = "{number}"

Step 5

Restore this modified 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\Explorer\Advanced
    • From: Hidden = "0" To: Hidden = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "1" To: HideFileExt = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
    • From: FullPath = "1" To: FullPath = "0"

Step 6

Search and delete this file

[ 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.  
  •  {path}\folder.htt

    Notes: Path is where it drops copies of itself and use the names of the folders where its located (i.e. D:\sample\sample.exe)

Step 7

Scan your computer with your Trend Micro product to delete files detected as Worm.Win32.WUKILL.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 the following Trend Micro Support pages for more information:


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