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Worm.Win64.FAUXPERSKY.AA

February 18, 2023
 Analysis by: Warren Adam Sto. Tomas
 ALIASES:

Trojan.SuspectCRC (Ikarus)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • 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.

It modifies certain registry entries to hide Hidden files.

  TECHNICAL DETAILS

File Size:

1,081,344 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

17 Feb 2023

Payload:

Drops files, Modifies system registry

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.

Autostart Technique

This Worm drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\taskmngr.lnk -> %AppData%\Kaspersky PURE v3.0\spoolsvc.exe detected as Worm.Win64.FAUXPERSKY.AA
  • %User Startup%\svhost.lnk -> executes %AppData%\Kaspersky PURE v3.0\svhost.exe detected as TrojanSpy.Win64.FAUXPERSKY.AB
  • %User Startup%\spoolsvc.lnk -> executes %AppData%\Kaspersky PURE v3.0\spoolsvc.exe detected as TrojanSpy.Win32.FAUXPERSKY.AA

Propagation

This Worm creates the following folders in all removable drives:

  • {Removable drive}:\Kaspersky PURE v3.0
  • {Removable drive}:\Kaspersky PURE v3.0\Vault
  • {Removable drive}:\Kaspersky PURE v3.0\System
  • All created folders have Read-Only, System, and Hidden attributes

Other Details

This Worm modifies the following registry entries to hide Hidden files:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

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

It does the following:

  • It copies the following files if they don't exist in the created folder yet ({Removable drive}:\Kaspersky PURE v3.0\System):
    • Files with .exe extension in %AppData%\Kaspersky PURE v3.0
  • It drops the following file in removable drives:
    • {Removable drive}:\{label of removable drive} ({size of removable drive}).lnk -> executes {Removable drive}:\Kaspersky PURE v3.0\System\winlogin.exe detected as TrojanSpy.Win32.FAUXPERSKY.AB
  • It sleeps for 5 seconds before proceeding with its routines. It repeats this cycle infinitely.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.262.08

FIRST VSAPI PATTERN DATE:

17 Feb 2023

VSAPI OPR PATTERN File:

18.263.00

VSAPI OPR PATTERN Date:

18 Feb 2023

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

Restart in Safe Mode

[ Learn More ]

Step 4

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • Hidden = 2
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = 0

Step 5

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.
  • %User Startup%\taskmngr.lnk
  • %User Startup%\svhost.lnk
  • %User Startup%\spoolsvc.lnk
  • {Removable drive}:\{label of removable drive} ({size of removable drive}).lnk

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.
  • {Removable drive}:\Kaspersky PURE v3.0
  • {Removable drive}:\Kaspersky PURE v3.0\Vault
  • {Removable drive}:\Kaspersky PURE v3.0\System

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Worm.Win64.FAUXPERSKY.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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