Filefinder
Table of Contents
Overview
Spyware:Win32/Filefinder is a specialized information-stealing trojan designed explicitly for data exfiltration and reconnaissance. Unlike broad stealers that grab browser passwords, Filefinder acts more like a targeted search engine for the attacker, silently scanning the compromised file system and network shares for specific documents, databases, or intellectual property, and uploading them to a remote server.
Understanding Filefinder (Spyware/Data Stealers)
To an end-user, Filefinder is invisible; it does not display ransom notes or degrade performance significantly. For an enterprise, it represents a critical data breach. Attackers deploy Filefinder after gaining initial access to map the network and extract high-value data (like `.docx`, `.pdf`, `.sql`, `.key`, or custom proprietary extensions) before deploying a louder payload like ransomware.
Execution and Data Exfiltration Mechanics
Filefinder is typically deployed manually by an attacker who has already achieved interactive access (e.g., via RDP or a backdoor). It is designed to run quietly in the background. It utilizes native Windows APIs (like `FindFirstFile` and `FindNextFile`) (`T1083`) to aggressively traverse local drives and mapped SMB shares (`T1039`). It is often configured with a specific list of target file extensions or keywords. When matching files are found, it copies them to a hidden staging directory (`T1074.001`), often compressing and encrypting them into a single archive (like a password-protected `.zip` or `.rar`) (`T1560.001`). Finally, it exfiltrates the archive to the attacker's C2 server using FTP, HTTP POST requests, or cloud storage APIs (`T1048.003`).
Indicators of Compromise & Impact
The impact is a severe breach of confidentiality and intellectual property theft. Host-based IoCs include EDR alerts for anomalous, high-volume file read operations by an unknown executable, the creation of large, encrypted archive files in temporary directories (staging), and unexpected scheduled tasks used for persistence. Network IoCs involve large outbound data transfers to unknown IP addresses or unrecognized cloud storage providers.
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 |
|---|---|---|---|
T1083 | File and Directory Discovery (Scanning the filesystem) | Discovery | ATT&CK ↗ |
T1074.001 | Data Staged: Local Data Staging (Copying files to a temp folder) | Collection | ATT&CK ↗ |
T1560.001 | Archive Collected Data: Archive via Utility (Compressing stolen data) | Collection | ATT&CK ↗ |
T1048.003 | Exfiltration Over Alternative Protocol | Exfiltration | ATT&CK ↗ |
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-NDF | Network Data Filtering | Isolate | T1048.003 | Inspect non-standard port traffic and block unauthorized ICMP or DNS tunneling protocols at the network perimeter. |
D3-FDA | File Directory Access Auditing | Detect | T1083 | Audit and alert on high-frequency recursive directory queries executed by non-system and unclassified binaries. |
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_FILEFINDER_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Filefinder"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "filefinder" 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 - Filefinder (Ransomware) Execution & Triage
id: 28effc23-a02b-56ae-a025-fe74b2b16bd0
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Filefinder malware family. Detects volume shadow copy deletion, boot status
tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/filefinder
- 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.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1560_001
- attack.t1074_001
- attack.t1048_003
- attack.t1083
logsource:
category: process_creation
product: windows
detection:
selection_process:
Image|endswith:
- \vssadmin.exe
- \wmic.exe
- \wbadmin.exe
- \bcdedit.exe
CommandLine|contains:
- delete shadows
- shadowcopy delete
- resize shadowstorage
- recoveryenabled no
- ignoreallfailures
condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: criticalTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_FILEFINDER_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Filefinder 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 = "filefinder" 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 endpoint immediately to halt any ongoing data exfiltration.
- Analyze the memory or the configuration file of the Filefinder executable to determine exactly which file types and directories were targeted.
- Review network egress logs to quantify the amount of data exfiltrated and identify the destination IP addresses/domains.
- Initiate incident response protocols for a confirmed data breach, as sensitive intellectual property or PII has likely been compromised.
What to Avoid
Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.
- Do not simply delete the malware and assume the incident is over; the primary damage (data theft) has likely already occurred, requiring a full breach investigation.
- Avoid rebooting the machine, as evidence of the staging directory or the active exfiltration connection may be lost.
References & External Analysis
- Search "filefinder" on VirusTotal (External Analysis)
- Search "filefinder" on Any.Run (Sandbox Sandbox)
- Search "filefinder" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Filefinder and what threat category does it belong to?
Filefinder is classified as a Ransomware. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments.
How does Filefinder establish persistence and evade defensive controls?
Filefinder typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks.
What are the essential incident response steps for mitigating a Filefinder compromise?
Security teams responding to Filefinder should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups.
What cryptographic algorithms and file targeting techniques does Filefinder employ during execution?
Filefinder typically leverages hybrid cryptographic architectures combining symmetric stream or block ciphers (such as AES-256 or ChaCha20) for rapid file encryption with asymmetric algorithms (such as RSA-2048 or Curve25519) to securely protect the session keys. It aggressively targets sensitive file extensions including corporate documents, databases, virtual disks, and backups while systematically executing commands to delete Volume Shadow Copies (vssadmin delete shadows /all /quiet) and disable system recovery options.
Are decryptors available for Filefinder, and what is the recommended recovery procedure?
Decryption availability for Filefinder depends on whether security researchers or law enforcement (such as the No More Ransom initiative) have recovered the master private keys or discovered flaws in its key generation routines. Victims should never pay the extortion demand, as payment fuels criminal operations without guaranteeing file restoration. The recommended recovery procedure entails isolating infected hosts, conducting forensic disk imaging, identifying the root access vector, and restoring validated systems from immutable offline backups.
How do I remove Filefinder from Windows?
Manual removal of Filefinder 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.
What are the main symptoms of a Filefinder infection?
Symptoms of Filefinder 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 Ransomwares
Want to prevent Filefinder and similar threats from compromising your organization? Read our comprehensive defensive guide: Ransomware Containment & Incident Response.
📣 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/filefinder.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.