Filerepmetagen

Overview

Behavior:Win32/Filerepmetagen is not a specific malware family, but a **Reputation-Based Heuristic Detection** utilized by modern antivirus and EDR solutions (specifically those leveraging cloud intelligence, like Avast or Microsoft). It flags executable files that are extremely new, very rarely seen in the global user base, lack a valid digital signature, and exhibit potentially suspicious characteristics (like being packed).

Understanding Filerepmetagen (Cloud Reputation)
To an end-user, this detection usually results in a file being blocked or quarantined immediately upon download, accompanied by a warning that the file is 'rare or suspicious'. For a security analyst, a Filerepmetagen alert is an indicator of an unknown, potentially zero-day threat, or simply a false positive caused by a developer compiling a new, internal, unsigned application.

Execution and Detection Mechanics
When a user attempts to download (`T1189`) or execute (`T1204.002`) an unknown file, the AV engine calculates the file's hash and metadata and queries a cloud-based threat intelligence database. If the database returns that the file has a 'low prevalence' (seen on very few machines globally), has a 'young age' (compiled very recently), lacks a verified publisher certificate (`T1553.002`), and perhaps originates from a low-reputation domain, the engine heuristically flags it as Filerepmetagen to protect the user proactively, even without a specific malware signature.

Indicators of Compromise & Impact
The impact depends entirely on the nature of the flagged file. If it is malware, the AV has successfully prevented an infection. Host-based IoCs are limited to the AV quarantine logs showing the block. EDR telemetry will detail the file's origin (e.g., downloaded via Chrome from a specific URL). Investigation requires determining if the file is a legitimate internal tool or a genuinely malicious dropper.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

MITRE D3FEND™ Defensive Countermeasures

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

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_FILEREPMETAGEN_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Filerepmetagen"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "filerepmetagen" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Filerepmetagen (Advanced Threat) Execution & Triage
id: c6fbf222-25ab-513b-b806-d0b6957c6d29
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Filerepmetagen 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/filerepmetagen
- 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.t1204_002
- attack.t1553_002
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_FILEREPMETAGEN_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Filerepmetagen 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 = "filerepmetagen" 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. Review the AV logs to identify the exact file that was quarantined, its original location on disk, and where it was downloaded from.
2. If the file is recognized as a legitimate, internally developed application, submit the hash to the AV vendor as a False Positive and sign the binary.
3. If the file is unknown, submit the quarantined sample to a dynamic analysis sandbox (like Any.Run or Joe Sandbox) to determine its actual behavior.
4. Educate developers to always digitally sign their compiled executables with a trusted corporate certificate to prevent reputation-based blocks.

What to Avoid

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

1. Do not blindly whitelist the file without investigating it; 'rare and unsigned' is the exact profile of a targeted spear-phishing payload.
2. Avoid disabling cloud-protection features in the AV; reputation-based blocking is critical for stopping zero-day ransomware before signatures exist.

References & External Analysis

• Search "filerepmetagen" on VirusTotal (External Analysis)
• Search "filerepmetagen" on Any.Run (Sandbox Sandbox)
• Search "filerepmetagen" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Advanced Threat)

Explore other documented threats in the same operational category:

• Gaofenquming
• Pckeeper
• Shadowbrokers
• Spywork
• Mycleanpc
• Smallhttp
• Taobao
• Extcrome

Machine-readable

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