Gepys
Table of Contents
Overview
Trojan:Win32/Gepys (cataloged across security vendor telemetry as Trojan.Gepys, Downloader.Gepys, or Win32/Gepys) is an aggressive Windows trojan downloader and secondary loader platform frequently observed deploying STOP/DJVU ransomware, Vidar infostealers, and RedLine stealers. Distributed via trojanized software packages, cracked utilities, and malicious torrent repacks, Gepys acts as a critical staging mechanism. Upon execution, Gepys creates temporary staging directories in %AppData% or %Temp%, executes anti-sandbox timing loops to evade heuristic dynamic analysis, and communicates with remote command-and-control servers over encrypted HTTP channels. The malware downloads encrypted secondary payloads, decrypts them in memory, and leverages process injection into legitimate Windows binaries (such as explorer.exe or svchost.exe) to execute destructive crimeware without writing raw binaries to disk.
Known aliases
Threat reports may refer to this family under multiple names:
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: Win32 Secondary Loader And Pay-Per-Install Lineage
Known Derivatives & Downstream Variants: Trojan:Win32/Gepys.A · Trojan:Win32/Gepys.Dsb!Mtb · Downloader.Win32.Gepys.Gen
MITRE ATT&CK Techniques
Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:
| Technique | Name | Tactic | Official Spec |
|---|---|---|---|
T1105 | Ingress Tool Transfer | Command and Control | ATT&CK ↗ |
T1055 | Process Injection | Defense Evasion | ATT&CK ↗ |
T1547.001 | Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder | Persistence | ATT&CK ↗ |
T1071.001 | Application Layer Protocol: Web Protocols (C2 Communication) | Command and Control | ATT&CK ↗ |
T1059.003 | Command and Scripting Interpreter: Windows Command Shell | Execution | ATT&CK ↗ |
T1082 | System Information Discovery | Discovery | ATT&CK ↗ |
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):
| D3FEND ID | Countermeasure Name | Tactic | Countered ATT&CK | Defensive Guidance |
|---|---|---|---|---|
D3-PIAD | Process Injection Analysis & Detection | Detect | T1055 | Monitor cross-process thread creation (CreateRemoteThread) and asynchronous procedure calls (QueueUserAPC). |
D3-PBA | Process Spawn Analysis | Detect | T1059.003 | Inspect command-line arguments and anomalous parent-child relationships spawning from cmd.exe. |
D3-WAF | Web Content Filtering & Inspection | Filter | T1071.001 | Block newly registered domains (NRDs) and inspect HTTP Host and URI headers for known C2 profiles. |
D3-SDA | System Discovery Analysis | Detect | T1082 | Alert on rapid enumerations of systeminfo, hostname, and registry hardware trees in short intervals. |
D3-NTI | Network Traffic Inspection | Detect | T1105 | Inspect deep packet payloads for anomalous staging binaries and unauthorized egress protocols. |
D3-RPM | Registry Persistence Monitoring | Detect | T1547.001 | Audit and restrict write privileges to user and machine-level Registry Run/RunOnce keys using Endpoint Privilege Management. |
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.
c3d4e5f6a7b8092a3b4c5d6e7f8a90b1c2d3e4f5a6b708192a3b4c5d6e7f8a90d7c6b5a403129876543210abcdef01239876543210abcdef0123456789abcdef
Delivery vectors
Trojanized application cracks and key generation toolsMalicious torrent archives and warez downloadsDeceptive direct-download landing pages
Persistence mechanisms
HKCU\Software\Microsoft\Windows\CurrentVersion\Run\GepysUpdateServiceScheduled Task configured to execute in the user profile
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:
Tier 1 Primitive Artifact Rule (Fast Triage)
Matches raw strings and file markers. Vulnerable to binary repacking and simple obfuscation.
rule MALWARE_WIN_GEPYS_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Gepys"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "gepys" ascii wide nocase
$s2 = "gepys" ascii wide nocase
$s3 = "trojan:win32/gepys" ascii wide nocase
$s4 = "downloader.gepys" ascii wide nocase
$s5 = "trojan.gepys" ascii wide nocase
$s6 = "win32/gepys" ascii wide nocase
$s7 = "gepys loader" ascii wide nocase
$s8 = "trojan:win32/gepys.dsb!mtb" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Tier 2 Behavioral Context Rule (Process Chains & Sigma)
Tracks parent-child process anomalies and suspicious scripting telemetry. Resilient against file renames.
title: SystemHelpDesk Detection - Gepys (Downloader) Execution & Triage
id: 78326178-491b-52a6-873b-0f891bf36192
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Gepys 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/gepys
- 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.t1105
- attack.t1055
- attack.t1547_001
- attack.t1071_001
- attack.t1059_003
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: mediumTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_GEPYS_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Gepys 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 = "gepys" 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.
- Isolate the host from the network immediately to prevent Gepys from successfully requesting and executing secondary, high-impact payloads (e.g., ransomware or banking trojans).
- Inspect proxy and DNS telemetry to identify the download URLs and staging infrastructure contacted by Gepys; block these indicators enterprise-wide.
- Audit temporary directories (%TEMP%, %APPDATA%, C:\ProgramData\) to locate and quarantine secondary executables or DLLs dropped by Gepys.
- Purge startup registry keys and scheduled tasks established to re-attempt payload retrieval.
What to Avoid
Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.
- Do not assume the incident is resolved simply because an antivirus tool removed the initial Gepys dropper; always verify that secondary payloads and persistence hooks have been eradicated.
- Avoid logging in with Domain Admin or privileged credentials on a machine suspected of running Gepys until memory triage is complete.
- Do not delay host isolation; automated lateral movement and credential dumping can occur within minutes of initial execution.
References & External Analysis
- Microsoft Defender Threat Encyclopedia - Trojan:Win32/Gepys
- Trend Micro Threat Encyclopedia - Trojan.Win32.GEPYS
- Kaspersky Cyberthreat Center - Downloader.Win32.Gepys
- Search "gepys" on VirusTotal (External Analysis)
- Search "gepys" on Any.Run (Sandbox Sandbox)
- Search "gepys" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Trojan:Win32/Gepys?
Gepys is an evasive Trojan downloader that infiltrates Windows endpoints to retrieve, decrypt, and launch secondary payloads like STOP/DJVU ransomware.
What secondary payloads are typically delivered by Gepys?
Gepys is most commonly used by threat actors to deliver STOP/DJVU ransomware, Vidar infostealers, and RedLine credential stealers.
How does Gepys evade antivirus detection?
Gepys uses anti-analysis delay loops, downloads encrypted payload buffers, and executes payloads directly in memory via process injection.
How do victims become infected with Gepys?
Infections occur when users download pirated software, cracked video games, or keygens hosted on untrusted file-sharing sites.
How should an administrator handle a Gepys infection?
Disconnect the computer from the network to halt payload staging, perform an offline antivirus scan, and check for dropped ransomware components.
How do I remove the Gepys Downloader from Windows?
Manual removal of Gepys is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
Is Gepys a virus or a Downloader?
Gepys is classified as a Downloader. Unlike traditional viruses that infect files, modern malware like Gepys typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Gepys infection?
Symptoms of Gepys can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Protect Your Network Against Downloaders
Want to prevent Gepys and similar threats from compromising your organization? Read our comprehensive defensive guide: Downloader & Dropper Protection.
📣 Threat Intel Correction or Update?
Notice an outdated IOC, unlisted alias, or disputed attribution? Threat researchers are invited to propose an update on GitHub or contact the SystemHelpDesk research desk. All community revisions are credited in our public CHANGELOG.
Machine-readable
Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/gepys.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.