Sfone

Overview

Sfone (cataloged across security vendors as Worm:Win32/Sfone, Worm.Win32.SFONE.B, and Trojan:Win32/Sfone!pz) is a self-propagating Windows worm and trojan loader first observed in active cybercrime campaigns around 2010. Engineered to compromise Windows endpoints through deceptive file naming and removable media propagation, Sfone frequently disguises its executable payload as screensavers, media files, or setup utilities. Once executed on a host, Sfone drops copies of itself into %APPDATA% and system temporary folders, modifies the Windows registry to ensure autostart execution upon user logon, and monitors connected drives to replicate across removable USB flash drives and network shares. The worm frequently weaponizes Windows Shell shortcut vulnerabilities such as CVE-2010-2568 to trigger automatic execution when users navigate infected folders. Beyond propagation, Sfone functions as an ingress tool transfer mechanism, beaconing out to remote command-and-control servers over HTTP/TCP to receive secondary instructions and stage additional malware payloads including adware, spyware, and trojan downloaders.

Known aliases

Threat reports may refer to this family under multiple names:

• Worm:Win32/Sfone
• Worm.Win32.SFONE
• Worm.Win32.SFONE.B
• Trojan:Win32/Sfone!pz
• Win32/Sfone

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Win32 Worm Frameworks

Known Derivatives & Downstream Variants: Sfone.A · Sfone.B · Sfone.Gen

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2010-2568 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b
• 4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c

Delivery vectors

• Infected USB storage devices utilizing malicious LNK shortcut files
• Compromised software distribution portals offering repackaged media tools

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SfoneService
• %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\sfone_upd.exe

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_SFONE_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Sfone"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "sfone" ascii wide nocase
        $s2 = "worm:win32/sfone" ascii wide nocase
        $s3 = "worm.win32.sfone" ascii wide nocase
        $s4 = "worm.win32.sfone.b" ascii wide nocase
        $s5 = "trojan:win32/sfone!pz" ascii wide nocase
        $s6 = "win32/sfone" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Sfone (Worm) Execution & Triage
id: c614b9e7-a626-5c07-a763-a7e18bf68caa
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Sfone malware family. Detects suspicious execution from temporary user
  directories with hidden window flags and background transfer utilities.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/sfone
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.worm
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1091
- attack.t1059_003
- attack.t1547_001
- attack.t1105
- attack.t1027
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \cmd.exe
    - \powershell.exe
    - \cscript.exe
    - \wscript.exe
    CommandLine|contains:
    - AppData\Local\Temp
    - -WindowStyle Hidden
    - /e:jscript
    - bitsadmin /transfer
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: medium

rule MALWARE_WIN_SFONE_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Sfone tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "sfone" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Isolate the compromised system from the network and disconnect all attached USB storage drives immediately.
2. Terminate suspicious processes executing from %APPDATA% or %TEMP% directories.
3. Remove malicious autostart registry keys under HKCU\Software\Microsoft\Windows\CurrentVersion\Run.
4. Scan and sanitize all removable flash media that were connected to the infected endpoint.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not connect infected USB flash drives to unmanaged workstations without write protection enabled.
2. Avoid opening unverified executable files masquerading as screensavers or document viewers.

References & External Analysis

• Microsoft Defender Security Intelligence - Worm:Win32/Sfone
• Trend Micro Threat Encyclopedia - Worm.Win32.SFONE.B
• NIST National Vulnerability Database - CVE-2010-2568
• Search "sfone" on VirusTotal (External Analysis)
• Search "sfone" on Any.Run (Sandbox Sandbox)
• Search "sfone" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Worm)

Explore other documented threats in the same operational category:

• Sasser
• Blasterx
• Koobface
• Pykspa
• Conficker
• Kolabc
• Blaster
• Skypespam

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/sfone.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.