Rubinurd

Overview

Rubinurd (cataloged by threat intelligence researchers and security vendors under identifiers including Trojan:Win32/Rubinurd, TrojanDownloader.Rubinurd, and Win32/Rubinurd) is a targeted Windows trojan downloader and staging agent active since 2011. Observed primarily in targeted cyber espionage and spearphishing campaigns targeting defense and governmental entities, Rubinurd was frequently delivered via weaponized Rich Text Format (RTF) and Word documents exploiting legacy memory corruption vulnerabilities (such as CVE-2010-3333 and CVE-2011-0611). Once executed, Rubinurd unpacks shellcode, unmaps target processes using NtUnmapViewOfSection, and injects clean staging code into host binaries. Rubinurd establishes encrypted beaconing to hardcoded command-and-control IP addresses and domains, serving as an initial access gateway to fetch, decrypt, and execute secondary surveillance backdoors—most notably the Taidoor and Simbot remote access trojans (RATs).

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Rubinurd
• TrojanDownloader:Win32/Rubinurd
• Win32/Rubinurd

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: Taidoor Malware Ecosystem

Known Derivatives & Downstream Variants: Rubinurd.A · Rubinurd.Simbot

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:

• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
• T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.

MITRE D3FEND™ Defensive Countermeasures

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

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.

• 1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b
• 3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d

Delivery vectors

• statement_analysis.doc
• rubinurd_stager.exe

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\RubinurdClient
• %AppData%\Rubinurd\svchost.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_RUBINURD_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Rubinurd"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "rubinurd" ascii wide nocase
        $s2 = "trojan:win32/rubinurd" ascii wide nocase
        $s3 = "trojandownloader:win32/rubinurd" ascii wide nocase
        $s4 = "win32/rubinurd" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Rubinurd (Downloader) Execution & Triage
id: d258259b-6a39-5b66-b772-9c562389dfbb
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Rubinurd 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/rubinurd
- 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.downloader
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1566_001
- attack.t1203
- attack.t1055_012
- attack.t1059_003
- attack.t1547_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_RUBINURD_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Rubinurd 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 = "rubinurd" 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 endpoint immediately to prevent Rubinurd from downloading and executing its secondary payloads (e.g., ransomware).
2. Audit the Windows Task Scheduler and Registry Run keys to identify and remove the Rubinurd persistence mechanisms.
3. Review firewall and proxy logs to identify the C2 domains Rubinurd attempted to contact, and block them enterprise-wide.
4. Capture a live memory image (RAM dump) to extract the injected Rubinurd modules and identify the secondary payloads.

What to Avoid

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

1. Do not close an incident simply because the initial Rubinurd dropper was quarantined; always verify if secondary payloads were downloaded.
2. Avoid relying solely on manual file deletion, as the injected processes will likely just recreate the dropped binaries.

References & External Analysis

• Contagio Malware Dump - Targeted Attack Rubinurd Analysis
• Snort Threat Rules - Trojan-Downloader.Win32.Rubinurd C2 Signatures
• Search "rubinurd" on VirusTotal (External Analysis)
• Search "rubinurd" on Any.Run (Sandbox Sandbox)
• Search "rubinurd" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Downloader)

Explore other documented threats in the same operational category:

• Bancteian
• Banload
• Chapak
• Nymeria
• Aim_Downloader
• Gepys
• Reconyc
• Nymaim

Machine-readable

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