Adduser

Overview

Adduser (classified in antivirus detection telemetry under designations including Backdoor:Win32/Adduser, Backdoor.Win32.Adduser, and Win32/Adduser) is a interactive remote access trojan and backdoor providing remote threat actors with unauthorized terminal control, file manipulation, and surveillance. Disseminated across enterprise networks and consumer workstations via social engineering, phishing attachments, malicious drive-by downloads, or weaponized software cracks, Adduser executes an initial reconnaissance phase upon system ingress. The binary evaluates host privileges, detects active hypervisors and sandbox environments to evade behavioral analysis, and establishes resilient autostart persistence by configuring registry keys under HKCU\Software\Microsoft\Windows\CurrentVersion\Run or registering background Windows services. Operational mechanics characteristic of this family include reverse shell connections, process hollowing, privilege escalation, and lateral movement reconnaissance. Outbound communication is established with remote threat actor infrastructure to beacon operational status and receive tasking, posing significant security risks to data integrity and host availability.

Known aliases

Threat reports may refer to this family under multiple names:

• Backdoor:Win32/Adduser
• Backdoor.Win32.Adduser
• Win32/Adduser

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:

• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.

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_ADDUSER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Adduser"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "adduser" ascii wide nocase
        $s2 = "backdoor:win32/adduser" ascii wide nocase
        $s3 = "backdoor.win32.adduser" ascii wide nocase
        $s4 = "win32/adduser" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Adduser (Backdoor) Execution & Triage
id: 8665ab40-ae44-5ade-9376-6752145843b2
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Adduser 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/adduser
- 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.backdoor
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1055
- attack.t1573
- attack.t1547_001
- attack.t1070
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_ADDUSER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Adduser 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 = "adduser" 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 disable (do not delete yet, for forensic purposes) any rogue accounts created by the tool.
2. Isolate the endpoint where the command was executed; if the tool was run successfully, the attacker already has SYSTEM-level access to that machine.
3. Audit all Active Directory and Local Administrator groups across the network to ensure no other unauthorized accounts have been created.
4. Conduct a full root-cause analysis to determine how the attacker gained the initial administrative privileges required to run the Adduser tool.

What to Avoid

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

1. Do not assume that deleting the rogue account removes the attacker; if they have `SYSTEM` access, they likely have deployed other backdoors (like scheduled tasks or web shells).
2. Avoid ignoring alerts for `net.exe /add`; while sometimes used by legitimate IT scripts, it is one of the most common techniques used by ransomware operators and APTs to maintain access.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Backdoor:Win32/Adduser
• Kaspersky Threat Intelligence - Backdoor.Win32.Adduser
• MITRE ATT&CK - Enterprise Techniques
• Search "adduser" on VirusTotal (External Analysis)
• Search "adduser" on Any.Run (Sandbox Sandbox)
• Search "adduser" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Backdoor)

Explore other documented threats in the same operational category:

• Keydoor
• Swrort
• Chopper
• Himera
• Younglotus
• Agobot
• Zxshell
• Amiboide

Machine-readable

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