Ircbrute

Overview

Trojan:Win32/Ircbrute is a classification for a botnet agent or worm that combines the command-and-control (C2) infrastructure of an Internet Relay Chat (IRC) botnet with aggressive network brute-forcing capabilities. Once it infects a host, it connects to an attacker-controlled IRC channel to receive commands and simultaneously begins scanning the internet or local network to brute-force weak credentials on exposed services (like SSH, RDP, or SQL databases) to spread the infection further (`T1110.001`).

Understanding Ircbrute
To an end-user, an Ircbrute infection might manifest as slow network performance due to the aggressive scanning. For a network administrator, it represents a significant, 'loud' threat. The infected machine becomes an active attacker, generating massive amounts of outbound traffic as it attempts to compromise other systems, potentially leading to the organization's IP address being blacklisted by external security services.

Execution and Propagation Mechanics
Upon execution, Ircbrute establishes persistence (usually via Registry Run keys) and initiates an outbound TCP connection to a hardcoded IRC server (often on port 6667 or alternative ports to evade simple firewall rules). Once joined to the C2 channel (`T1071.001`), the bot receives a list of target IP ranges and a dictionary of common usernames and passwords. The malware then executes multi-threaded brute-force attacks (`T1110.001`) against services like SMB (TCP 445), RDP (TCP 3389), or MSSQL (TCP 1433). Upon a successful login, it uses tools like PsExec or WMI to copy itself to the new victim and execute, expanding the botnet.

Indicators of Compromise & Impact
The primary impact is network congestion, participation in a botnet, and the compromise of other internal servers. Network IoCs are glaring: persistent outbound TCP connections to external IRC servers, coupled with massive spikes in outbound scanning and login attempts (Failed Login Events - Event ID 4625) targeting internal or external infrastructure. Host IoCs include the malware executable (often hidden in `%SystemRoot%` or `%Temp%`) and corresponding persistence mechanisms.

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:

• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.

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_IRCBRUTE_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Ircbrute"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "ircbrute" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Ircbrute (Trojan) Execution & Triage
id: a6063372-75a1-5197-84cd-80d81ab5b817
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Ircbrute 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/ircbrute
- 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.t1547_001
- attack.t1046
- attack.t1110_001
- 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_IRCBRUTE_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Ircbrute 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 = "ircbrute" 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. Segment the infected host immediately to stop the outbound brute-force attacks and prevent lateral movement.
2. Block outbound IRC traffic (TCP port 6667, 6660-6669) at the perimeter firewall to sever the C2 connection.
3. Review Active Directory logs for Event ID 4625 (Failed Logon) to identify which accounts were targeted by the brute-force attack and reset compromised passwords.
4. Enforce strict password complexity and multi-factor authentication (MFA) on all externally facing services (RDP, VPN) to mitigate brute-forcing.

What to Avoid

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

1. Do not ignore the infection as a simple 'adware' issue; an active Ircbrute infection means your network is being used to attack others.
2. Avoid cleaning the host without investigating network logs; you must identify if the brute-force attack successfully compromised other internal machines.

References & External Analysis

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

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Tasker
• Ausiv
• Oficla
• Separ
• Dnschanger
• Wintrim
• Adwapper
• Multijoiner

Machine-readable

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