Yiwanzhushou

Overview

Executive Summary

Infection Vector and Technical Capabilities

• Aggressive Browser Hijacking: The software installs persistent extensions across Chrome, Firefox, and Edge. It forcefully modifies the default homepage, search engine, and new tab page to route all traffic through affiliate-monetized search engines controlled by the adware developers.
• System Watchdogs and Rootkit Tactics: Yiwanzhushou frequently installs background "watchdog" services that actively monitor the registry and browser settings. If a user attempts to remove the extension or change their homepage back to a legitimate search engine, the watchdog service instantly reinstalls the adware configurations.
• Ad Injection and Overlay: It injects its own JavaScript into legitimate websites, overlaying pages with intrusive pop-up ads, sliding banners, and embedded video advertisements, significantly degrading system performance and user experience.

Threat Assessment

Incident Response and Remediation

• Safe Mode and Process Termination: Due to the aggressive watchdog services, it is often necessary to boot the infected machine into Windows "Safe Mode" to prevent the adware's defense mechanisms from launching before attempting uninstallation.
• Targeted Anti-Malware Scan: Standard antivirus often ignores PUPs. Utilize a reputable enterprise anti-malware solution (specifically tuned for Adware removal) to scan for and remove the deeply embedded registry keys and scheduled tasks.
• Browser Factory Reset: Following the removal of the underlying files, a full factory reset of all installed web browsers is absolutely required to purge the malicious extensions and hijacked settings.

Known aliases

Threat reports may refer to this family under multiple names:

• Adware.Yiwanzhushou
• PUP.Yiwanzhushou
• Win32/Adware.Hijacker

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:

• T1185: Enforce strong MFA and use browser isolation or hardened browsers for sensitive financial or administrative portals to defeat session hijacking.

MITRE D3FEND™ Defensive Countermeasures

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

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_YIWANZHUSHOU_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Yiwanzhushou"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "yiwanzhushou" ascii wide nocase
        $s2 = "adware.yiwanzhushou" ascii wide nocase
        $s3 = "pup.yiwanzhushou" ascii wide nocase
        $s4 = "win32/adware.hijacker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Yiwanzhushou (Ransomware) Execution & Triage
id: 2ce034a4-3c20-5dfb-a63f-1241f3ca8874
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Yiwanzhushou malware family. Detects volume shadow copy deletion, boot
  status tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/yiwanzhushou
- 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.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1185
- attack.t1176
- attack.t1546_015
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \vssadmin.exe
    - \wmic.exe
    - \wbadmin.exe
    - \bcdedit.exe
    CommandLine|contains:
    - delete shadows
    - shadowcopy delete
    - resize shadowstorage
    - recoveryenabled no
    - ignoreallfailures
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: critical

rule MALWARE_WIN_YIWANZHUSHOU_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Yiwanzhushou 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 = "yiwanzhushou" 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. Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Yiwanzhushou from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.
2. Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Yiwanzhushou symmetric encryption keys or uncompiled payload components may still reside in memory.
3. Audit process execution logs and terminate active scripting interpreters (e.g. PowerShell, CMD, WScript) or commands executing 'vssadmin.exe delete shadows' or 'wbadmin' used by Yiwanzhushou to inhibit recovery.
4. Investigate the initial compromise vector (such as exposed RDP instances, spearphishing attachments, or vulnerable edge gateways) and enforce an immediate credential reset for all compromised Active Directory accounts.
5. Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Yiwanzhushou binary and related persistence hooks are eradicated.

What to Avoid

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

1. Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Yiwanzhushou.
2. Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.
3. Do not connect clean backup drives or external storage to the affected network until Yiwanzhushou eradication is completely verified.

References & External Analysis

• Search "yiwanzhushou" on VirusTotal (External Analysis)
• Search "yiwanzhushou" on Any.Run (Sandbox Sandbox)
• Search "yiwanzhushou" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Remoh
• Scomma
• Dnguard
• Pcvark
• Launcher
• Hiru
• Newheur
• Otezinu

Machine-readable

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