Netbus
Table of Contents
Overview
NetBus is one of the earliest, most legendary, and influential Remote Access Trojans in personal computing history, originally created in March 1998 by Swedish computer programmer Carl-Fredrik Neikter. Written in Borland Delphi to run on Microsoft Windows 95, 98, and Windows NT, NetBus was initially marketed by its author as a harmless remote administration tool and prank utility. However, alongside the contemporaneous Back Orifice released by the Cult of the Dead Cow (cDc), NetBus ignited the modern era of remote administrative backdoors and network-borne malware exploitation. NetBus operated using an unauthenticated or password-protected client-server architecture: the server executable ('patch.exe') listened on TCP port 12345 (with port 12346 used for keylogger streaming). Once connected, the graphical client console gave attackers total control: opening and closing CD-ROM trays, swapping mouse buttons, taking screenshots, capturing real-time keystrokes, displaying popup messages, recording microphone audio, and executing arbitrary system commands. NetBus also played a landmark role in cyber law: in a famous 1999 Swedish criminal trial, a university professor was acquitted of possessing illegal material after forensic analysis demonstrated an unknown attacker had compromised his computer via NetBus and planted the files.
Known aliases
Threat reports may refer to this family under multiple names:
Threat Actor Attribution
Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.
- Carl-Fredrik Neikter (Swedish Author, March 1998) High confidence
Basis: Authored and publicly released by Swedish developer Carl-Fredrik Neikter in 1998. NetBus became the foundation for legal precedents regarding remote trojan defenses in computer crime trials in Europe and the United States. [source]
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: Netbus V1.53 · Netbus V1.60 · Netbus V1.70 · Netbus Pro V2.0
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: Restrict execution of scripting languages such as PowerShell, VBScript, or Python to authorized administrators. Enforce Script Block Logging.
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-STM | Scheduled Job & Task Monitoring | Detect | T1053 | Monitor Event ID 4698 (A scheduled task was created) and inspect schtasks.exe command-line arguments. |
D3-SEA | Script Execution Analysis | Detect | T1059 | Analyze script block syntax and command arguments at runtime to detect malicious automation. |
Command & Control (C2) and Network Profile
How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.
| Protocols | TCP, Plaintext Command Protocol, Reverse Connection (NetBus 2.0 Pro) |
|---|---|
| Observed ports | 12345, 12346, 20034 |
| Infrastructure model | Direct inbound TCP listening socket on port 12345 (patch.exe), responding to plaintext ASCII command strings from the NetBus graphical client. |
| Identifiable from traffic alone | Unrated |
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.
4f2e96d2ff86e7a2df25b84c8a29a6cf7d853177699317585f6e80b27ef3e6ffb1b4c330f89fa6d165f973e20e8b22a08846c4f09a5b3a8634860b0ec89c565d
Delivery vectors
IRC DCC file transfers and peer-to-peer file-sharing networksExecutable binders bundling patch.exe inside games, pornographic media, or utility installers
Persistence mechanisms
HKLM\Software\Microsoft\Windows\CurrentVersion\Run entry pointing to patch.exeModification of system.ini (shell=explorer.exe patch.exe) in Windows 95/98 environments
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_NETBUS_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Netbus"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "netbus" ascii wide nocase
$s2 = "netbus" ascii wide nocase
$s3 = "netbus pro" ascii wide nocase
$s4 = "patch.netbus" ascii wide nocase
$s5 = "backdoor.netbus" ascii wide nocase
$s6 = "trojan.netbus" 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 - Netbus (Rat) Execution & Triage
id: b98b28f6-3021-5e05-b314-c5b24cfa0b35
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Netbus malware family. Detects unauthorized persistence creation via Windows
Registry Run keys, scheduled tasks, and privilege escalation indicative of RAT installations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/netbus
- 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.rat
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1056_001
- attack.t1113
- attack.t1125
- attack.t1071_001
- attack.t1547_001
logsource:
category: process_creation
product: windows
detection:
selection_process:
Image|endswith:
- \reg.exe
- \schtasks.exe
- \cmd.exe
- \powershell.exe
CommandLine|contains:
- \CurrentVersion\Run
- /create /tn
- bypass -enc
- net user /add
- net localgroup administrators
condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: highTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_NETBUS_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Netbus 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 = "netbus" 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.
- Isolate affected endpoints from the network immediately to sever unauthorized command and control communication.
- Identify and terminate active Netbus binaries and associated parent-child process chains.
- Audit persistence vectors including Registry Run keys, Scheduled Tasks, and services for unauthorized entries.
- Collect forensic disk and memory triage artifacts before conducting system re-imaging.
What to Avoid
Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.
- Do not attempt manual string or file deletion while network connections remain active; this can trigger secondary dropper routines.
- Avoid restoring from backups without verifying that the backup snapshot predates initial Netbus installation.
References & External Analysis
- US Department of Justice CCIPS - Computer Crime Legal Precedents
- CERT Coordination Center - NetBus Vulnerability Advisory
- Swedish Legal Archives - Landmark 1999 Trojan Defense Case
- Search "netbus" on VirusTotal (External Analysis)
- Search "netbus" on Any.Run (Sandbox Sandbox)
- Search "netbus" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is NetBus?
NetBus is a pioneering Remote Access Trojan created in 1998 by Carl-Fredrik Neikter that allowed users to remotely control Windows computers over TCP.
What ports did NetBus use?
By default, the NetBus server listened for inbound remote commands on TCP port 12345 and used port 12346 for raw keystroke logging.
What landmark legal precedent did NetBus establish?
In a 1999 Swedish criminal trial, a defendant was acquitted when computer forensics proved that an unknown attacker had planted illegal files on his computer using NetBus without his knowledge.
What capabilities did the NetBus client provide?
NetBus allowed attackers to capture screens and keystrokes, eject CD-ROM trays, record microphone audio, view and edit files, and execute programs.
How is NetBus detected and removed?
Detect NetBus by monitoring for open listening ports on TCP 12345, inspecting startup Run registry keys for 'patch.exe', and deploying standard endpoint antivirus software.
How do I remove the Netbus Rat from Windows?
Manual removal of Netbus 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 Netbus a virus or a Rat?
Netbus is classified as a Rat. Unlike traditional viruses that infect files, modern malware like Netbus typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Netbus infection?
Symptoms of Netbus 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 Rats
Want to prevent Netbus and similar threats from compromising your organization? Read our comprehensive defensive guide: Backdoor & RAT Protection for Businesses.
📣 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/netbus.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.