3Proxy

Overview

3Proxy (classified in antivirus detection telemetry under designations including Trojan:Win32/3Proxy, Trojan.Win32.3Proxy, and Win32/3Proxy) is a multi-stage trojan engineered to disguise itself as legitimate software, execute unauthorized commands, and coordinate with external command-and-control infrastructure. Disseminated across enterprise networks and consumer workstations via social engineering, phishing attachments, malicious drive-by downloads, or weaponized software cracks, 3Proxy executes an initial reconnaissance phase upon system ingress. The binary evaluates host privileges, detects active hypervisors and sandbox environments to evade behavioral analysis, and establishes resilient autostart persistence by configuring registry keys under HKCU\Software\Microsoft\Windows\CurrentVersion\Run or registering background Windows services. Operational mechanics characteristic of this family include deceptive executable masquerading, registry run key autostart, system telemetry gathering, and remote C2 beaconing. Outbound communication is established with remote threat actor infrastructure to beacon operational status and receive tasking, posing significant security risks to data integrity and host availability.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/3Proxy
• Trojan.Win32.3Proxy
• Win32/3Proxy

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:

• 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):

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_3PROXY_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for 3Proxy"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "3proxy" ascii wide nocase
        $s2 = "trojan:win32/3proxy" ascii wide nocase
        $s3 = "trojan.win32.3proxy" ascii wide nocase
        $s4 = "win32/3proxy" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - 3proxy (Trojan) Execution & Triage
id: 769b5f32-a757-5b1a-a683-5e04b02b2f9d
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the 3proxy 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/3proxy
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1027
- attack.t1547_001
- attack.t1071_001
- attack.t1105
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_3PROXY_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for 3Proxy 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 = "3proxy" 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. Isolate the endpoint to immediately sever the proxy connections being routed through the machine.
2. Identify and terminate the running `3proxy` process, and delete the associated executable and `.cfg` configuration file.
3. Audit Scheduled Tasks, Registry Run keys, and Services to remove the persistence mechanism that launches the proxy.
4. Investigate how the attacker gained initial access (e.g., exposed RDP, weak passwords) and remediate the vulnerability to prevent reinfection.

What to Avoid

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

1. Do not assume 3proxy is inherently malware; check with system administrators to ensure it wasn't installed legitimately for network routing (though rare on standard endpoints).
2. Avoid relying solely on file deletion, as the attacker may still have the initial access backdoor (like a web shell or compromised credentials) used to install it.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Trojan:Win32/3Proxy
• Kaspersky Threat Intelligence - Trojan.Win32.3Proxy
• MITRE ATT&CK - Enterprise Techniques
• Search "3proxy" on VirusTotal (External Analysis)
• Search "3proxy" on Any.Run (Sandbox Sandbox)
• Search "3proxy" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Corebot
• Ymkfawdgfnmi
• Adwind
• Picsys
• Cerberus
• Synrat
• Lockpos
• Hostseditor

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/3proxy.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.