Yuner
Table of Contents
Overview
Yuner (documented in threat intelligence research and antivirus catalogs under Virus:Win32/Yuner, Worm:Win32/Yuner, and W32/Yuner) is a landmark polymorphic file-infecting virus and worm that originated in China in 2009. Engineered for aggressive lateral spread, Yuner systematically scans local hard drives, network shares, and removable USB drives for Portable Executable (PE) files. It infects host executables by appending its polymorphic decryptor stub to the last section of legitimate PE files, redirecting the address of entry point (OEP) to execute the viral body before transferring control back to the host program. In addition to parasitic file infection, Yuner creates autorun.inf files on removable media, connects to remote IRC/HTTP servers for distributed denial-of-service (DDoS) commands, and terminates antivirus software processes to maintain persistent dominance over infected systems.
Known aliases
Threat reports may refer to this family under multiple names:
Family Pedigree & Lineage
Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:
Known Derivatives & Downstream Variants: Virus:Win32/Yuner.A · Virus:Win32/Yuner.B · Worm:Win32/Yuner.Gen
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1091 · T1080 · T1562.001 · T1498 · T1547.001
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-RMC | Removable Media Access Control | Harden | T1091 | Enforce Group Policy settings disabling Windows autorun and block execution permissions on removable USB storage media. |
D3-TR | Traffic Rate Limiting | Isolate | T1498 | Deploy BGP Flowspec and edge scrubbing proxies to automatically throttle volumetric SYN and UDP reflection attacks. |
D3-RPM | Registry Persistence Monitoring | Detect | T1547.001 | Audit and restrict write privileges to user and machine-level Registry Run/RunOnce keys using Endpoint Privilege Management. |
D3-STA | Security Tool Anti-Tamper Enforcement | Harden | T1562.001 | Block unauthorized modification of antivirus registry flags and prevent stopping security agent services. |
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_YUNER_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Yuner"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "yuner" ascii wide nocase
$s2 = "virus:win32/yuner" ascii wide nocase
$s3 = "worm:win32/yuner" ascii wide nocase
$s4 = "virus.win32.yuner" ascii wide nocase
$s5 = "win32/yuner" ascii wide nocase
$s6 = "w32/yuner" ascii wide nocase
$s7 = "virus:win32/yuner.a" 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 - Yuner (File Infector) Execution & Triage
id: e56087ce-5539-5ff4-8882-e8b6027fc4f6
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Yuner 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/yuner
- 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.file-infector
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1091
- attack.t1080
- attack.t1562_001
- attack.t1498
- attack.t1547_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_YUNER_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Yuner 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 = "yuner" 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
}References & External Analysis
- Microsoft Defender Threat Encyclopedia - Virus:Win32/Yuner.A
- Trend Micro Threat Encyclopedia - Virus.Win32.Yuner
- Kaspersky Securelist - Virus.Win32.Yuner In-Depth
- Search "yuner" on VirusTotal (External Analysis)
- Search "yuner" on Any.Run (Sandbox Sandbox)
- Search "yuner" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Virus:Win32/Yuner?
Yuner is a polymorphic file-infecting virus and worm that appends malicious code to Windows PE executables and spreads across USB drives and network shares.
How does Yuner infect executable files?
It appends its polymorphic code to the last section of host PE files and redirects the initial entry point to run the virus before host application execution.
How does Yuner spread to external systems?
It copies itself to removable USB flash drives alongside an autorun.inf file and scans local networks for open, writable SMB shares.
What secondary botnet capabilities does Yuner possess?
Yuner connects to remote command-and-control servers to participate in coordinated distributed denial-of-service (DDoS) flooding attacks.
How can infected PE files be cleaned without corrupting host programs?
Use specialized antivirus disinfection utilities that strip the appended section and restore the original entry point (OEP), or restore clean files from backups.
How do I remove the Yuner File_Infector from Windows?
Manual removal of Yuner 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 Yuner a virus or a File_Infector?
Yuner is classified as a File_Infector. Unlike traditional viruses that infect files, modern malware like Yuner typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Yuner infection?
Symptoms of Yuner 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 File_Infectors
Want to prevent Yuner and similar threats from compromising your organization? Read our comprehensive defensive guide: Think You've Been Hacked? What To Do First.
📣 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/yuner.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.