Blaster

Overview

Blaster (also widely cataloged as MSBlast, Lovsan, and Poosan) is one of the most famous and destructive self-propagating computer worms in internet history, first detected on August 11, 2003. Propagating at machine speed across the global IPv4 address space without requiring any email opening, attachment execution, or user interaction, Blaster scanned random IP subnets on TCP port 135 to find unpatched endpoints running Microsoft Windows 2000 and Windows XP. When an open port was found, Blaster exploited a critical stack buffer overflow in the Distributed Component Object Model (DCOM) interface of the Windows RPCSS service (CVE-2003-0352 / MS03-026). Once code execution was achieved, Blaster spawned an unauthenticated remote command shell on TCP port 4444 and instructed the compromised endpoint to download the full worm binary ('msblast.exe') from the attacking host via Trivial File Transfer Protocol (TFTP) over UDP port 69. The worm payload contained hidden text strings taunting Microsoft's founder ('billy gates why do you make this possible ? Stop making money and fix your software!!'). Additionally, Blaster was programmed to launch a coordinated distributed denial-of-service (DDoS) SYN flood against port 80 of windowsupdate.com starting on August 15, 2003, forcing Microsoft to temporarily take the Windows Update portal offline to protect global internet routing infrastructure. Blaster infected hundreds of thousands of computers worldwide within days, severely degrading internet traffic and accelerating the creation of modern Windows security baselines.

Known aliases

Threat reports may refer to this family under multiple names:

• MSBlast
• Lovsan
• Poosan
• W32.Blaster.Worm
• Win32/Blaster

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: Blaster_A · Blaster_B · Welchia_Nachi_Counterworm

MITRE ATT&CK Techniques

This family has been observed using the following ATT&CK techniques: T1210 · T1059 · T1547.001 · T1498

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):

Exploited Vulnerabilities (CVEs)

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

• CVE-2003-0352 — 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.

• 2b6a5db21d00f7e44a42e5d7db69b466ea2084c55bc66c5d1e2e1329c31b312b
• a17387f5df2307ef086915091219b671a172776c59b67195721118182969b761

Delivery vectors

• Autonomous network worm propagation exploiting DCOM RPC buffer overflow CVE-2003-0352 over TCP port 135
• Automated TFTP download on UDP port 69 spawning command shell on TCP port 4444

Persistence mechanisms

• HKLM\Software\Microsoft\Windows\CurrentVersion\Run entry pointing to msblast.exe in %SYSTEM32%
• Spawning of autonomous background scanning threads on system boot

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_BLASTER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Blaster"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "blaster" ascii wide nocase
        $s2 = "msblast" ascii wide nocase
        $s3 = "lovsan" ascii wide nocase
        $s4 = "poosan" ascii wide nocase
        $s5 = "w32.blaster.worm" ascii wide nocase
        $s6 = "win32/blaster" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Blaster (Worm) Execution & Triage
id: 1ce5084e-801d-5307-a86f-5e138dbccfb7
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Blaster 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/blaster
- 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.t1210
- attack.t1059
- attack.t1547_001
- attack.t1498
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_BLASTER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Blaster 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 = "blaster" 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
}

References & External Analysis

• Microsoft Security Bulletin MS03-026: Buffer Overrun In RPC Interface Could Allow Code Execution
• CISA Alert TA03-223A: Blaster Worm
• CERT Coordination Center Advisory CA-2003-20: W32/Blaster worm
• Search "blaster" on VirusTotal (External Analysis)
• Search "blaster" on Any.Run (Sandbox Sandbox)
• Search "blaster" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Worm)

Explore other documented threats in the same operational category:

• Skypespam
• Lolbot
• Vbs_Worm_Generator
• Perinet
• Benjamin
• Beebone
• Mira
• Cambot

Machine-readable

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