Skeeyah

Overview

Trojan:Win32/Skeeyah is a widely encountered family of evasive trojan loaders and multi-stage droppers documented extensively in Microsoft Windows Defender telemetry. Specifically engineered to circumvent heuristic and signature-based endpoint defenses, Skeeyah executables employ multi-layered polymorphic packing, anti-sandbox sleep drift verification, and code virtualization. Upon validating that it is running in an authentic end-user operating environment, Skeeyah executes process hollowing or dynamic link library (DLL) injection into legitimate Windows processes (such as explorer.exe or svchost.exe). From this concealed vantage point, it acts as a flexible stage-two downloader, retrieving and executing secondary malware payloads including credential stealers, cryptocurrency miners, and ransomware.

Known aliases

Threat reports may refer to this family under multiple names:

• Skeeyah
• Trojan:Win32/Skeeyah
• Trojan.Skeeyah
• Win32/Skeeyah
• Skeeyah Dropper
• Trojan.Win32.Skeeyah

Threat Actor Attribution

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

• Underground Cybercrime Developers 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: Skeeyah.A · Skeeyah Process Hollowing Loader · Skeeyah Polymorphic Build

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.
• 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-2015-1641 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2017-11882 — 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.

• 5f6a7b8091a2b3c4d5e6f708192a3b4c5d6e7f8091a2b3c4d5e6f708192a3b4c
• 2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e

Delivery vectors

• drive_by_downloads
• spearphishing_attachments

Persistence mechanisms

• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
• Windows Task Scheduler Job Creation

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_SKEEYAH_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Skeeyah"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "skeeyah" ascii wide nocase
        $s2 = "skeeyah" ascii wide nocase
        $s3 = "trojan:win32/skeeyah" ascii wide nocase
        $s4 = "trojan.skeeyah" ascii wide nocase
        $s5 = "win32/skeeyah" ascii wide nocase
        $s6 = "skeeyah dropper" ascii wide nocase
        $s7 = "trojan.win32.skeeyah" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Skeeyah (Trojan) Execution & Triage
id: 7dd2e23b-f0a1-5ce1-83ee-5c1f07a7b59a
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Skeeyah 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/skeeyah
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1055_012
- attack.t1027
- attack.t1497_001
- attack.t1105
- 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_SKEEYAH_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Skeeyah 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 = "skeeyah" 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 compromised endpoints to stop secondary payload downloads and lateral movement attempts.
2. Analyze running processes with behavioral EDR tools to identify hollowed explorer.exe and svchost.exe instances.
3. Extract volatile memory to recover unencrypted second-stage download URLs and C2 IP addresses.
4. Deploy security updates patching Microsoft Office memory corruption flaws CVE-2015-1641 and CVE-2017-11882.

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 static antivirus hashes; Skeeyah's multi-layered crypter changes with each compiled binary.
2. Avoid running unverified executables downloaded from public internet forums or torrent networks.
3. Never disable operating system real-time behavioral protection mechanisms.

References & External Analysis

• Microsoft Security Intelligence: Trojan:Win32/Skeeyah Heuristic Guidance
• Trend Micro Threat Encyclopedia: Trojan.Skeeyah Analysis
• NIST National Vulnerability Database CVE-2017-11882
• Search "skeeyah" on VirusTotal (External Analysis)
• Search "skeeyah" on Any.Run (Sandbox Sandbox)
• Search "skeeyah" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Byfh
• Zlob
• Fakeff
• Genericrxge
• Gamsoft
• Injeber
• Bayrob
• Picsys

Machine-readable

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