Sinowal

Overview

Trojan:Win32/Sinowal (universally known in the security industry as **Torpig**) is a legendary, highly advanced banking trojan that peaked in the late 2000s. Sinowal is infamous for being one of the first widespread malware families to successfully weaponize a Master Boot Record (MBR) rootkit (often utilizing the Mebroot bootkit component) to achieve complete, invisible, and virtually unremovable persistence on infected Windows machines.

Understanding Sinowal (Torpig)
To an infected user, Sinowal was entirely invisible. The computer booted normally, and online banking sessions appeared legitimate. For a threat intelligence analyst, Sinowal represents a historical milestone in malware sophistication. Because it infected the MBR (the very first sector of the hard drive read by the BIOS), the malware executed *before* the Windows operating system even loaded. This allowed Sinowal to comprehensively hook the OS kernel from below, rendering it invisible to standard antivirus software running within Windows.

Execution and MBR Rootkit Mechanics
Sinowal was primarily distributed via drive-by downloads utilizing Exploit Kits (like MPack or Neosploit) on compromised websites (`T1189`). Once the exploit succeeded, the dropper payload executed. It immediately wrote malicious code directly to the hard drive's Master Boot Record (Sector 0) (`T1542.003`). Upon the next reboot, the Sinowal bootkit executed before Windows. It patched the OS loader in memory (`T1014`), ensuring that its core banking trojan components were injected into critical system processes (like `explorer.exe` and web browsers) as soon as Windows started (`T1055`). Sinowal then monitored all web traffic (`T1185`), utilizing sophisticated Man-in-the-Browser (MitB) web injects to steal banking credentials, credit card numbers, and bypass two-factor authentication (`T1056.002`).

Indicators of Compromise & Impact
The impact was massive financial fraud; Sinowal operators famously stole millions of banking credentials. Detection was exceptionally difficult. Standard file scans would find nothing because the malicious code resided outside the Windows file system. Incident responders had to rely on specialized MBR scanners or EDR behavioral alerts flagging unauthorized raw disk access (writing to `\.\PhysicalDrive0`). Network logs showing encrypted communication to known Torpig C2 domains (often utilizing fast-flux DNS) were the most reliable IoC.

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:

• T1056.002: Monitor for unauthorized keylogging, screen capturing, or web browser API hooking. Deploy EDR to detect API hooking.
• T1185: Enforce strong MFA and use browser isolation or hardened browsers for sensitive financial or administrative portals to defeat session hijacking.

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_SINOWAL {
    meta:
        description = "Detects Sinowal (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "sinowal" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Sinowal Activity
id: 736e6043c7669474d7ce4ebc3b3b6d2f
status: experimental
description: Detects generic indicators of the sinowal malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*sinowal*"
    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; an active Sinowal infection means the attacker is likely monitoring banking sessions and capturing all keystrokes.
2. Do NOT trust the operating system or standard antivirus removal tools; a bootkit operates below the OS and cannot be reliably removed from within Windows.
3. To remediate, you must boot the machine from a clean, offline recovery environment (like a Windows PE USB) and use the `bootrec /fixmbr` command (or similar utilities) to overwrite the malicious Master Boot Record with a clean one.
4. After fixing the MBR, a complete wipe and reinstallation of the operating system is still highly recommended to ensure all secondary payloads are destroyed.

What to Avoid

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

1. Do not assume the infection is gone just because an antivirus scanner says the system is clean; MBR rootkits hide themselves from scanners.
2. Avoid relying solely on file-based IoCs; focus on network telemetry and raw disk access alerts.

References & External Analysis

• Search "sinowal" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Lmir
• Spamer
• Rescoms
• Indigorose
• Sz4Aaw

Machine-readable

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