Rustock

Overview

Rootkit:Win32/Rustock (internally designated as Costrat) was an extraordinarily sophisticated, stealthy kernel-mode rootkit and spam botnet active between 2006 and its dramatic federal takedown in March 2011. Comprising over 1.5 million infected Windows systems globally, Rustock was estimated at its peak to be responsible for pumping between 30% and 40% of the entire world's daily email spam volume (generating more than 30 billion unsolicited messages per day advertising illicit pharmaceuticals, counterfeit watches, and stock manipulation schemes). Architected by a master rootkit developer operating under the pseudonym 'Cosma' (associated in research with Russian national Dmitrij Sergeevich Nechvolod), Rustock executed as a deeply embedded Windows kernel driver that subverted the System Service Dispatch Table (SSDT), modified direct kernel object tables, and injected threads directly into system processes without dropping conventional on-disk files. In March 2011, Microsoft's Digital Crimes Unit (DCU), partnered with Pfizer, FireEye, and the US Marshals Service, executed Operation b107 under a landmark federal court order, simultaneously raiding command data centers in seven US cities, severing upstream ISP links, and permanently disabling the botnet.

Known aliases

Threat reports may refer to this family under multiple names:

• Rustock
• Costrat
• Rootkit.Win32.Rustock
• Spam-Mailbot.Rustock

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• Dmitrij Sergeevich Nechvolod (Cosma) High confidence
  Basis:
• Russian Cybercrime Spambot Underground High confidence
  Basis:

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: Rustock.A (2006) · Rustock.B (Advanced Rootkit Driver) · Rustock.C (Rc4 Encryption & Self-Defense)

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.
• T1566.002: Inspect email links for known malicious domains and use link-rewriting services for time-of-click analysis.

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-2006-0003 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2008-2244 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

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.

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.

• 4345eb6eeecb321a59051d95dc48e77a9497e68db30058b73ad6ba16dc681428
• 93ab0a927ec0bc1d34c2ab79d67e5ff825c88b64e5257e841893d5f308e7ef9e

Delivery vectors

• trojan_droppers
• drive_by_downloads

Persistence mechanisms

• Kernel Service Driver
• SSDT Hooking Architecture

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_RUSTOCK_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Rustock"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "rustock" ascii wide nocase
        $s2 = "rustock" ascii wide nocase
        $s3 = "costrat" ascii wide nocase
        $s4 = "rootkit.win32.rustock" ascii wide nocase
        $s5 = "spam-mailbot.rustock" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Rustock (Advanced Threat) Execution & Triage
id: c45146d0-1a0b-5b2f-a2e4-97f27e969c2a
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Rustock malware family. Detects proxy execution, reflective DLL loading,
  and remote command injection associated with modular enterprise backdoors.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/rustock
- 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.advanced-threat
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1014
- attack.t1055
- attack.t1566_002
- attack.t1071_001
- attack.t1114_001
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \powershell.exe
    - \cmd.exe
    - \rundll32.exe
    - \regsvr32.exe
    CommandLine|contains:
    - DownloadString
    - IEX(
    - '/s /n /u /i:'
    - sc create
    - start-process
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: high

rule MALWARE_WIN_RUSTOCK_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Rustock 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 = "rustock" 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. Execute offline system kernel scans using specialized rootkit removal environments (Windows PE).
2. Block outbound SMTP connections (port 25) from general client endpoints on perimeter egress firewalls.
3. Isolate compromised endpoints to prevent internal network scanning and email credential harvesting.
4. Apply security updates to close legacy Windows operating system vulnerabilities CVE-2006-0003 and CVE-2008-2244.

What to Avoid

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

1. Do not rely solely on user-mode task manager utilities to detect running rootkit processes.
2. Avoid allowing unrestricted outbound port 25 traffic from unmanaged client workstations.
3. Do not execute unknown installer programs downloaded from unverified third-party websites.

References & External Analysis

• Microsoft On the Issues: Operation b107 - Rustock Botnet Takedown
• FireEye Labs Rustock Technical Teardown
• NIST National Vulnerability Database CVE-2006-0003
• Search "rustock" on VirusTotal (External Analysis)
• Search "rustock" on Any.Run (Sandbox Sandbox)
• Search "rustock" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Advanced Threat)

Explore other documented threats in the same operational category:

• Gocloudnet
• Incredimail
• Hiddeninstall
• Turla
• Multibar
• Tencent
• Monder
• Pullupdate

Machine-readable

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