Kolab

Overview

Kolab (cataloged across security vendors as Worm:Win32/Kolab, Net-Worm.Win32.Kolab, WORM_KOLABC, and W32/Kolab) is a prolific Windows network worm and backdoor trojan first discovered in 2008. Designed to build distributed botnets for distributed denial-of-service (DDoS) attacks, spam campaigns, and secondary malware distribution, Kolab propagates autonomously across local area networks (LANs) and removable USB flash drives. The worm exploits legacy network vulnerabilities, notably MS08-067 (CVE-2008-4250 Server Service buffer overflow) and MS06-040 (CVE-2006-3439 Server Service vulnerability), as well as open administrative SMB shares using weak credentials. When a host is compromised, Kolab injects its core thread into Windows system processes (such as svchost.exe and explorer.exe), disables Windows Firewall and security center services, and opens encrypted IRC or TCP reverse shell channels to attacker-controlled command-and-control servers. Through this persistent backdoor, operators can issue arbitrary shell commands, capture sensitive user keystrokes, harvest network credentials, and download secondary ransomware or banking payloads.

Known aliases

Threat reports may refer to this family under multiple names:

• Worm:Win32/Kolab
• Net-Worm.Win32.Kolab
• WORM_KOLABC
• W32/Kolab
• Trojan.Win32.Kolab

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: Modular Win32 Network Worm Framework · Irc Botnet Propagation Engine

Known Derivatives & Downstream Variants: Kolab.A · Kolab.C · Kolab.D · Kolab.Gen

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.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.

MITRE D3FEND™ Defensive Countermeasures

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

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2008-4250 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2006-3439 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

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.

• c2e4f6a8b0d1e3f5a7b9c1d3e5f7a9b1c3d5e7f9a1b3c5d7e9f1a3b5c7d9e1f3
• d3f5a7b9c1e2f4a6b8d0e2f4a6b8c0d2e4f6a8b0c2d4e6f8a0b2c4d6e8f0a2b4

Delivery vectors

• Network worm replication exploiting SMB buffer overflow vulnerabilities (MS08-067)
• Infection of removable USB media using autorun.inf and hidden system binaries

Persistence mechanisms

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\WinUpdateSvc
• %SYSTEM32%\drivers\etc\hosts modification
• %SYSTEM32%\kolab_srv.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_KOLAB_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Kolab"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "kolab" ascii wide nocase
        $s2 = "worm:win32/kolab" ascii wide nocase
        $s3 = "net-worm.win32.kolab" ascii wide nocase
        $s4 = "worm_kolabc" ascii wide nocase
        $s5 = "w32/kolab" ascii wide nocase
        $s6 = "trojan.win32.kolab" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Kolab (Worm) Execution & Triage
id: 22e06405-20bc-5cdc-aa3a-1994a90ae007
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Kolab 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/kolab
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-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.worm
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1547_001
- attack.t1021_002
- attack.t1071_001
- attack.t1105
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_KOLAB_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Kolab 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 = "kolab" 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. Isolate the compromised endpoint from the network immediately to sever active IRC command-and-control channels and halt lateral worm replication.
2. Terminate rogue threads injected into svchost.exe and purge dropped worm binaries from %SYSTEM32% and %TEMP%.
3. Audit and block lateral SMB (port 445) and NetBIOS (port 139) traffic between internal workstation segments.
4. Verify that security patches for MS08-067 (CVE-2008-4250) and SMB security baselines are enforced across all network hosts.

What to Avoid

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

1. Do not leave exposed administrative SMB shares accessible with blank or default administrative passwords.
2. Avoid connecting infected USB storage devices to unpatched systems without disabling AutoRun and AutoPlay.

References & External Analysis

• Microsoft Defender Security Intelligence - Worm:Win32/Kolab
• Trend Micro Threat Encyclopedia - WORM_KOLABC
• Kaspersky Threat Intelligence - Net-Worm.Win32.Kolab
• Search "kolab" on VirusTotal (External Analysis)
• Search "kolab" on Any.Run (Sandbox Sandbox)
• Search "kolab" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Worm)

Explore other documented threats in the same operational category:

• Pluto
• Lamer
• Mogoogwi
• Mabezat
• Lovgate
• Koobface
• Xorer
• Sasser

Machine-readable

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