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 the 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.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_IRCBRUTE {
    meta:
        description = "Detects Ircbrute (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "ircbrute" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Ircbrute Activity
id: b07e48c89c145eaadb74346cd30edd5b
status: experimental
description: Detects generic indicators of the ircbrute malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*ircbrute*"
    condition: selection
level: medium

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)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Maxdriver
• Bitmin
• Virledi
• Arcdoor
• Bunitu

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/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.