Smshoax
Table of Contents
Overview
Trojan:AndroidOS/Smshoax is a prevalent classification of mobile malware specifically designed to commit financial fraud by silently subscribing the victim to premium-rate SMS services or making unauthorized phone calls. While primarily targeting the Android ecosystem, variations exist across mobile platforms. This threat leverages the billing mechanisms of telecommunications carriers, directly draining the victim's prepaid balance or inflating their monthly phone bill.
Understanding SMS Hoax Fraud
To an end-user, the infection is often imperceptible until they receive their monthly phone bill showing exorbitant charges for 'premium text services' or international calls they never made. For security analysts, this represents a highly lucrative, automated monetization scheme. The malware acts as a silent proxy, interacting with carrier billing APIs without the user's knowledge or consent.
Execution and Fraud Mechanics
Smshoax is typically distributed via third-party app stores, disguised as legitimate applications (like games, wallpaper apps, or adult content) (`T1533`). Upon installation (`T1204`), the malware requests excessive permissions, specifically `SEND_SMS`, `READ_SMS`, and `CALL_PHONE` (`T1614.001`). Once granted, it operates in the background. It utilizes its C2 server to receive a list of premium-rate numbers. It then silently sends SMS messages to these numbers (`T1629`). Crucially, to hide its activity from the user, the malware intercepts and immediately deletes the confirmation SMS messages sent back by the premium service or the carrier (`T1562.001`), ensuring the user remains completely unaware they have been subscribed to a recurring, expensive service.
Indicators of Compromise & Impact
The primary impact is direct financial loss for the user. Technical IoCs on the mobile device include an unknown application holding SMS and Phone permissions. Behavioral IoCs include unexpected drops in prepaid mobile balances, unexplained premium charges on phone bills, and the device sending outbound SMS messages to shortcodes (e.g., 5-digit numbers) without user interaction.
MITRE ATT&CK Techniques
Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:
MITRE D3FEND™ Defensive Countermeasures
Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):
| D3FEND ID | Countermeasure Name | Tactic | Countered ATT&CK | Defensive Guidance |
|---|---|---|---|---|
D3-STA | Security Tool Anti-Tamper Enforcement | Harden | T1562.001 | Block unauthorized modification of antivirus registry flags and prevent stopping security agent services. |
D3-MPP | Mobile Platform Integrity Verification | Harden | T1629 | Deploy mobile threat defense (MTD) agents to detect tampering with OS security daemons. |
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:
Tier 1 Primitive Artifact Rule (Fast Triage)
Matches raw strings and file markers. Vulnerable to binary repacking and simple obfuscation.
rule MALWARE_WIN_SMSHOAX_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Smshoax"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "smshoax" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Tier 2 Behavioral Context Rule (Process Chains & Sigma)
Tracks parent-child process anomalies and suspicious scripting telemetry. Resilient against file renames.
title: SystemHelpDesk Detection - Smshoax (Trojan) Execution & Triage
id: 830b0bdb-229f-5e5e-ab8c-3ee2245ec3c5
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Smshoax 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/smshoax
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1629
- attack.t1614_001
- attack.t1533
- attack.t1562_001
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: mediumTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_SMSHOAX_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Smshoax 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 = "smshoax" 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.
- Immediately boot the Android device into Safe Mode to prevent third-party applications from running.
- Navigate to the Application Manager, locate the suspicious app (often the most recently installed game or utility), and uninstall it.
- Contact the mobile telecommunications carrier immediately to report the fraud, dispute the charges, and request a hard block on all premium-rate SMS billing.
- Review and revoke excessive permissions (like `SEND_SMS`) for all remaining applications on the device.
What to Avoid
Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.
- Do not ignore small, unexplained charges on a mobile bill; SMS fraud often starts small to avoid detection before ramping up.
- Avoid downloading applications from unverified, third-party app stores or side-loading APKs from unknown websites.
References & External Analysis
- Search "smshoax" on VirusTotal (External Analysis)
- Search "smshoax" on Any.Run (Sandbox Sandbox)
- Search "smshoax" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Smshoax and what threat category does it belong to?
Smshoax is classified as a Trojan. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments.
How does Smshoax establish persistence and evade defensive controls?
Smshoax typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks.
What are the essential incident response steps for mitigating a Smshoax compromise?
Security teams responding to Smshoax should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups.
What secondary payloads and staging behaviors are commonly associated with Smshoax?
Smshoax frequently operates as a loader or dropper designed to establish a foothold before downloading and executing secondary high-impact malware payloads. Depending on the threat actor's objectives, these dropped modules can range from ransomware and banking injects to modular infostealers and remote management backdoors.
How can security operations teams effectively detect and hunt for Smshoax across enterprise endpoints?
Defenders should hunt for Smshoax by deploying behavioral endpoint detection and response (EDR) rules that monitor suspicious process spawning (such as cmd.exe or powershell.exe spawned from office documents or temporary directories), anomalous outbound network connections from non-browser binaries, and unauthorized modifications to Windows Run keys and scheduled task registries.
How do I remove the Smshoax Trojan from Windows?
Manual removal of Smshoax is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
Is Smshoax a virus or a Trojan?
Smshoax is classified as a Trojan. Unlike traditional viruses that infect files, modern malware like Smshoax typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Smshoax infection?
Symptoms of Smshoax can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Protect Your Network Against Trojans
Want to prevent Smshoax and similar threats from compromising your organization? Read our comprehensive defensive guide: Banking Trojan Protection for Businesses.
📣 Threat Intel Correction or Update?
Notice an outdated IOC, unlisted alias, or disputed attribution? Threat researchers are invited to propose an update on GitHub or contact the SystemHelpDesk research desk. All community revisions are credited in our public CHANGELOG.
Machine-readable
Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/smshoax.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.