Doyo

Overview

Adware:Win32/Doyo is a pervasive Potentially Unwanted Application (PUA) and Adware variant whose primary objective is aggressive monetization through unauthorized advertising injection and browser hijacking. It severely degrades the user experience by hijacking search queries, inserting interstitial ads into legitimate websites, and tracking browsing habits to build marketing profiles, which are then sold to third-party data brokers.

Understanding the Doyo Threat
To an end-user, Doyo manifests as a sudden, drastic slowdown in web browsing, accompanied by unprompted pop-ups and a changed default search engine. For a corporate IT department, Doyo is a major productivity sink and a security risk, as the injected advertisements frequently link to tech support scams, phishing sites, or exploit kits capable of dropping more severe malware.

Execution and Browser Hijacking Mechanics
Doyo is almost exclusively distributed via Pay-Per-Install (PPI) bundling networks (`T1189`). When a user downloads freeware (like a PDF converter) from an untrustworthy site, the Doyo installer is silently executed in the background (`T1204.002`). It establishes persistence by creating scheduled tasks (`T1053.005`) and dropping malicious extensions into all installed browsers (Chrome, Edge, Firefox) (`T1176`). It modifies the browser's shortcut files (`.lnk`) to append arguments that force the browser to open Doyo-controlled domains upon launch. It then intercepts web traffic to inject its own HTML/JavaScript advertisements over legitimate page content.

Indicators of Compromise & Impact
The primary impact is the loss of user productivity and potential exposure to secondary threats. Host-based IoCs include EDR alerts for the modification of browser `.lnk` files on the Desktop or Taskbar, and the presence of unfamiliar, heavily obfuscated browser extensions. Network IoCs include a high volume of HTTP/HTTPS traffic to known adware tracking domains (often fast-flux domains) and a sudden drop in traffic to the organization's approved default search provider.

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):

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_DOYO_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Doyo"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "doyo" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Doyo (Advanced Threat) Execution & Triage
id: a362989f-e007-5ef0-b971-e6b657a02e12
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Doyo malware family. Detects proxy execution, reflective DLL loading, and
  remote command injection associated with modular enterprise backdoors.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/doyo
- https://malware-families-catalog.systemhelpdesk.com/defensive/backdoor-rat-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.advanced-threat
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1204_002
- attack.t1562_001
- attack.t1189
- attack.t1176
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \powershell.exe
    - \cmd.exe
    - \rundll32.exe
    - \regsvr32.exe
    CommandLine|contains:
    - DownloadString
    - IEX(
    - '/s /n /u /i:'
    - sc create
    - start-process
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: high

rule MALWARE_WIN_DOYO_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Doyo 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 = "doyo" 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. Use the Windows Control Panel to uninstall the primary Doyo application and any bundled software installed on the same date.
2. Run an enterprise-grade Adware/PUA removal tool (like Malwarebytes) to strip the persistent browser extensions and scheduled tasks.
3. Manually inspect and repair all web browser shortcuts (`.lnk` files) to ensure they point directly to the legitimate executable, without appended URLs.
4. Reset all web browsers to their factory default settings to clear hijacked homepages and search engine configurations.

What to Avoid

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

1. Do not allow users local administrator rights; standard users generally cannot install the system-level services required by persistent adware like Doyo.
2. Avoid ignoring adware infections; the infrastructure used to deliver Doyo is frequently repurposed to deliver ransomware.

References & External Analysis

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

Frequently Asked Questions

Related Threats (Category: Advanced Threat)

Explore other documented threats in the same operational category:

• Visicom
• Netcat
• Logicielsespions
• Molebox
• Torntv
• Speesipro
• Familykeylogger
• Hostmodifier

Machine-readable

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