Subseven

Overview

SubSeven (also widely known as Sub7, Backdoor.SubSeven, and Sub7 Gold) is one of the most culturally iconic and technologically influential Remote Access Trojans in computing history. Created in 1999 by a hacker using the pseudonym 'Mobman', SubSeven served as the direct successor to earlier Windows backdoors like NetBus and Back Orifice, offering a graphical client interface and advanced remote administration capabilities. Written in Delphi, SubSeven allows unauthorized operators to connect to infected Windows 9x, NT, and 2000 machines over TCP (typically listening on default ports 27374 or 1243). The backdoor provided a vast array of surveillance and administrative features, including real-time keystroke logging, webcam streaming, audio recording, screen capture, file management, registry editing, CD-ROM tray manipulation, port redirection, and denial-of-service packet flooding. SubSeven also featured an automated notification engine, alerting the attacker via ICQ, IRC, or email whenever an infected machine connected to the internet.

Known aliases

Threat reports may refer to this family under multiple names:

• Sub7
• Backdoor.SubSeven
• Sub7 Gold
• Trojan.SubSeven
• Backdoor:Win32/SubSeven
• Sub7 2.2

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Win32 Backdoor Era

Known Derivatives & Downstream Variants: Sub7 2.1 · Sub7 2.2 · Sub7 Gold · Sub7 Legends

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.
• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.
• T1113: Monitor for frequent or unauthorized screen captures or clipboard reads. Restrict background applications from accessing desktop APIs.
• T1125: Restrict access to local camera or microphone APIs. Utilize endpoint protection that monitors hardware access.

MITRE D3FEND™ Defensive Countermeasures

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

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a
• 3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d

Delivery vectors

• Vintage IRC DCC file transfers, ICQ messaging, and pirated software game cracks
• Deceptive executable binders combining the Sub7 server with legitimate games or utilities

Persistence mechanisms

• HKLM\Software\Microsoft\Windows\CurrentVersion\Run\SubSevenServer
• win.ini [windows] run=server.exe

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_SUBSEVEN_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Subseven"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "subseven" ascii wide nocase
        $s2 = "sub7" ascii wide nocase
        $s3 = "backdoor.subseven" ascii wide nocase
        $s4 = "sub7 gold" ascii wide nocase
        $s5 = "trojan.subseven" ascii wide nocase
        $s6 = "backdoor:win32/subseven" ascii wide nocase
        $s7 = "sub7 2.2" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Subseven (Trojan) Execution & Triage
id: 764c742f-329b-5bc1-be91-d0dd0007d7eb
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Subseven 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/subseven
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1547_001
- attack.t1113
- attack.t1125
- attack.t1071_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: medium

rule MALWARE_WIN_SUBSEVEN_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Subseven 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 = "subseven" 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. Disconnect the affected host from the network to terminate active attacker sessions on port 27374.
2. Kill the server process (frequently named server.exe, nodll.exe, or hidden under legitimate system names).
3. Clean malicious entries from the Windows registry Run keys and win.ini/system.ini configuration files.
4. Delete the server binary from the Windows System directory and perform a full antivirus scan.

What to Avoid

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

1. Do not execute software files sent over IRC, instant messaging services, or unverified download sites.
2. Avoid exposing Windows workstations to the public internet without router NAT and firewall protection.

References & External Analysis

• Trend Micro Threat Encyclopedia - Backdoor.SubSeven
• Broadcom Symantec Security Response - Backdoor.SubSeven
• Search "subseven" on VirusTotal (External Analysis)
• Search "subseven" on Any.Run (Sandbox Sandbox)
• Search "subseven" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Korplug
• Enfal
• Fakeplayer
• Spesr
• Sofacy
• Drooptroop
• Trickbot
• Virtu

Machine-readable

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