Filerepmalware

Overview

Win32:FileRepMalware is a broad, generic heuristic detection primarily utilized by the Avast and AVG antivirus engines. It does not identify a specific malware family; rather, it indicates that a downloaded executable has an exceptionally low 'reputation score' within the vendor's global threat intelligence cloud.

Understanding FileRepMalware
To the end-user, this is a standard antivirus block, often occurring immediately after downloading a file. For a security analyst, a 'FileRepMalware' detection means the AV engine lacks a specific signature for the file, but blocked it based on metadata. The 'Reputation' score is calculated using factors such as: How many users globally have downloaded this file? (If it's very few, it's suspicious). Is the file digitally signed by a trusted publisher? How new is the file? Was it downloaded from a domain known for hosting malware?

Execution and Threat Hunting
Because it is a reputation-based heuristic, the infection vector varies. It is frequently triggered by newly compiled, custom malware (which inherently has zero reputation), very rare adware, or sometimes, poorly coded legitimate software (False Positives). If the file executes, threat hunters must rely entirely on EDR telemetry to trace its behavior. Did it attempt to inject code (`T1055`)? Did it establish an outbound connection to an unknown IP (`T1105`)? The AV engine blocked it *preventatively* before it could exhibit these behaviors.

Forensic Analysis & Impact
The impact is dependent on the true nature of the payload. Incident responders cannot rely on the 'FileRepMalware' name for attribution. The immediate focus must be on obtaining the quarantined binary. Dynamic analysis in a sandbox (like Cuckoo) is essential to determine if the low-reputation file is genuinely malicious (e.g., a novel trojan) or simply a benign, unsigned application.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1036: Monitor for executable files running from unusual paths or with deceptive names. Use EDR to detect process masquerading.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
• T1566.002: Inspect email links for known malicious domains and use link-rewriting services for time-of-click analysis.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_FILEREPMALWARE {
    meta:
        description = "Detects Filerepmalware (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "filerepmalware" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Filerepmalware Activity
id: 340a94922e48f324d79ba05314bcaf1e
status: experimental
description: Detects generic indicators of the filerepmalware malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*filerepmalware*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Verify that the AV engine successfully quarantined the low-reputation file and that no child processes were spawned prior to the block.
2. Extract the quarantined binary securely and submit it to a dynamic analysis sandbox or VirusTotal to determine its true behavior.
3. Review EDR logs to trace the origin of the file (e.g., was it downloaded via a browser, dropped by a macro, or executed from a USB?).
4. If the file is determined to be a False Positive (e.g., a custom internal corporate app), whitelist its hash in the AV console.

What to Avoid

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

1. Do not assume the threat is minor simply because it lacks a specific family name; reputation blocks often catch novel, previously unseen zero-day threats.
2. Avoid closing the incident without determining *how* the suspicious binary arrived on the endpoint.

References & External Analysis

• Search "filerepmalware" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Autoitscript
• Windang
• Lovgate
• Staser
• Godzilla

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/api/filerepmalware.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.