Sfone

Overview

Trojan:Win32/Sfone is a highly targeted information stealer and stealthy backdoor engineered to quietly exfiltrate sensitive data while maintaining long-term persistence on compromised endpoints.

Understanding Sfone
To the victim, Sfone provides zero visual indication of infection. For threat intelligence analysts, Sfone represents a specialized espionage tool. Unlike noisy botnets, it is often utilized in targeted campaigns where the primary goal is the prolonged, silent extraction of proprietary documents, keystrokes, and active directory credentials rather than immediate financial extortion.

Execution and Evasion Strategies
Sfone is typically delivered via highly tailored spearphishing campaigns containing weaponized Office documents. Upon execution, it performs extensive environment checks, querying the registry for known sandbox artifacts and halting execution if a debugger is detected. Once validated, it drops a heavily obfuscated DLL into the <code>%AppData% directory. It achieves persistence by employing DLL Search Order Hijacking against legitimate system executables or creating a hidden scheduled task. It communicates with its Command-and-Control (C2) server using custom encryption over HTTPS to blend in with normal corporate web traffic.

Indicators of Compromise & Impact
The impact of Sfone is a total compromise of confidentiality. Incident responders should monitor for anomalous, persistent HTTPS connections originating from legitimate processes (like svchost.exe) to unknown or newly registered IP addresses. Memory forensics is critical to extract the decrypted Sfone payload and identify the specific C2 domains. Dropped, highly entropic .dat files in the user profile directory (used to stage stolen data before exfiltration) are strong IoCs.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Tactical Mitigations

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

• T1056.001: Implement Endpoint Detection and Response (EDR) to monitor for suspicious API calls related to keystroke interception. Enforce Multi-Factor Authentication (MFA) to render stolen passwords useless.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_SFONE {
    meta:
        description = "Detects Sfone (trojan_generic)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "sfone" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Sfone Activity
id: 9bac82f73b9fd2d0d20fe15428b6d19a
status: experimental
description: Detects generic indicators of the sfone malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*sfone*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Instantly isolate the endpoint from the network to sever the attacker's interactive, remote-control session.
2. Capture a full forensic memory image of the machine to extract the decrypted Sfone payload and its C2 configuration.
3. Force a global password reset for all user accounts that accessed the machine, assuming total endpoint and credential compromise.
4. Rebuild the operating system from a known-clean image, as Sfone is known to deploy secondary rootkits to maintain access.

What to Avoid

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

1. Do not leave the machine connected to the network during triage; the attacker has live access and will likely destroy evidence or move laterally.
2. Avoid relying solely on static signatures, as Sfone is frequently re-packed and obfuscated for each targeted campaign.

References & External Analysis

• Search "sfone" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan_generic)

Explore other malware families in the same category:

• Reconyc
• Gepys
• Byfh
• Mikey
• Laqma

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/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.