Vtflooder

Overview

VtFlooder (tracked across enterprise threat intelligence as Trojan:Win32/VtFlooder, Tool:Win32/VtFlooder, and Spammer:Win32/VtFlooder) is an automated cloud submission flooding utility and reputation poisoning tool analyzed by Microsoft Defender and Trend Micro. VtFlooder was engineered by underground cybercrime actors and crypter developers to repeatedly submit dummy, modified, or synthetic PE binaries to public cloud multiscanner APIs (such as VirusTotal) via automated REST interface calls. By rotating egress HTTP/SOCKS proxies and dynamically mutating binary hashes while embedding decoy benign metadata strings, VtFlooder attempts to exhaust API ingestion rate limits, pollute vendor automated machine-learning classifiers, and manipulate detection consensus metrics. The tool contains multi-threaded network workers, an embedded list of public proxy nodes, and routines to generate random entropy padded files to overwhelm cloud sandbox queues. System defenders monitor for high-frequency automated HTTP API transmissions from unauthorized internal endpoints.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/VtFlooder
• Tool:Win32/VtFlooder
• Spammer:Win32/VtFlooder
• Tool.Win32.VtFlooder
• Troj/VtFlood

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: Cloud_Reputation_Poisoning_Toolkits

Known Derivatives & Downstream Variants: Vtflooder.A · Vtspammer.Gen

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:

• 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):

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.

• b7a8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8
• c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9

Delivery vectors

• Underground hacker forums and malware developer crypter packages
• Direct operator staging onto compromised developer workstations

Persistence mechanisms

• Operator-managed standalone executable execution without auto-start installation
• Optional scheduled task creation via AT or Task Scheduler for recurring flood campaigns

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_VTFLOODER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Vtflooder"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "vtflooder" ascii wide nocase
        $s2 = "trojan:win32/vtflooder" ascii wide nocase
        $s3 = "tool:win32/vtflooder" ascii wide nocase
        $s4 = "spammer:win32/vtflooder" ascii wide nocase
        $s5 = "tool.win32.vtflooder" ascii wide nocase
        $s6 = "troj/vtflood" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Vtflooder (Pua Tool) Execution & Triage
id: 05be464b-9728-57c3-bb53-be568ebb0e1c
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Vtflooder 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/vtflooder
- 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.pua-tool
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1105
- attack.t1071_001
- attack.t1090_003
- attack.t1027_001
- attack.t1498_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_VTFLOODER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Vtflooder 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 = "vtflooder" 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. Terminate active VtFlooder network threads and delete binary binaries from staging locations.
2. Enforce egress network proxy filtering to block non-whitelisted automated API submissions to security scanners.
3. Inspect perimeter proxy logs for recurring high-frequency POST requests to threat analysis platforms.
4. Run a full EDR telemetry scan to identify underlying dropper mechanisms or crypter toolkits on the host.

What to Avoid

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

1. Do not permit internal development endpoints to run unmonitored automated API submission scripts using public proxies.
2. Avoid ignoring high-volume outbound POST alerts to public malware analysis portals.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Tool:Win32/VtFlooder Profile
• Trend Micro Threat Encyclopedia - Tool.Win32.VtFlooder Details
• NIST National Vulnerability Database - CVE-2015-1641
• Search "vtflooder" on VirusTotal (External Analysis)
• Search "vtflooder" on Any.Run (Sandbox Sandbox)
• Search "vtflooder" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Pua Tool)

Explore other documented threats in the same operational category:

• Winwrapper
• Cheatengine
• Winactivator
• Gamehack
• Oxypumper

Machine-readable

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