Worm.Win32.SFONE.SM

October 07, 2025

Analysis by: Christian Daniel Jr. Dy Quiangco

PLATFORM:

Windows

OVERALL RISK RATING:

DAMAGE POTENTIAL:

DISTRIBUTION POTENTIAL:

REPORTED INFECTION:

INFORMATION EXPOSURE:

Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes

OVERVIEW

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.

TECHNICAL DETAILS

File Size: 950036 bytes

File Type: EXE

Memory Resident: Yes

Initial Samples Received Date: 29 Sep 2025

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 copies of itself into the affected system:

{Folder Name}\{File Name}.{Extension}.exe
- Where {Folder Name} includes any of the following substrings:
- Where {File Name} is a random combination of the following strings:
- And where {Extension} is any of the following:

It drops the following files:

%System Root%\debug.txt

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

It adds the following processes:

{Malware Path}\{Malware Name}

Autostart Technique

This Worm creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
mssrv32 = %Windows%\mssrv.exe

SOLUTION

Minimum Scan Engine: 9.800

FIRST VSAPI PATTERN FILE: 15.981.80

FIRST VSAPI PATTERN DATE: 09 Jul 2020

VSAPI OPR PATTERN File: 15.983.00

VSAPI OPR PATTERN Date: 10 Jul 2020

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

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.

Step 5

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.

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Worm.Win32.SFONE.SM. 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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Worm.Win32.SFONE.SM

OVERVIEW

TECHNICAL DETAILS

SOLUTION

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