Farfli

Overview

Trojan:Win32/Farfli is a sophisticated Remote Access Trojan (RAT) derived from the leaked Gh0st RAT codebase, customized extensively by Chinese state-sponsored advanced persistent threat groups (including APT10 / MenuPass and Winnti Group / APT41) for targeted cyber espionage campaigns. Farfli replaces standard Gh0st RAT network communication magic signatures with customized five-byte protocol headers (such as 'HTTPS', 'HEART', 'QQQQQ') and non-standard network ports to bypass network intrusion detection system (NIDS) signatures. Operating stealthily within compromised government, aerospace, and defense environments, Farfli injects into core Windows processes (such as explorer.exe and svchost.exe), providing operators with comprehensive remote desktop control, interactive command shells, file exfiltration, keystroke recording, and webcam/audio surveillance.

Known aliases

Threat reports may refer to this family under multiple names:

• Farfli
• Trojan:Win32/Farfli
• Backdoor.Farfli
• Farfli RAT
• Backdoor.Win32.Farfli
• Win32/Farfli

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• APT10 (MenuPass / Stone Panda) High confidence
  Basis:
• Winnti Group (APT41) Medium confidence
  Basis:

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: Gh0St

Known Derivatives & Downstream Variants: Farfli V1.X · Farfli Custom Header Variant · Farfli Dynamic Dns Build

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:

• T1056.001: Implement Endpoint Detection and Response (EDR) to monitor for suspicious API calls related to keystroke interception. Enforce Multi-Factor Authentication (MFA) to render stolen passwords useless.
• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.
• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.
• T1113: Monitor for frequent or unauthorized screen captures or clipboard reads. Restrict background applications from accessing desktop APIs.
• T1125: Restrict access to local camera or microphone APIs. Utilize endpoint protection that monitors hardware access.

MITRE D3FEND™ Defensive Countermeasures

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

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2012-0158 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2017-11882 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

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.

• a1b2c3d4e5f60718293a4b5c6d7e8f90123456789abcdef0123456789abcdef0
• 4f53cda12f8645b23e7589c31b53995f9c46d338a0695029a2632bca578b8438

Delivery vectors

• spearphishing_attachments
• exploit_document_payloads

Persistence mechanisms

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
• Windows Service Registration

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_FARFLI_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Farfli"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "farfli" ascii wide nocase
        $s2 = "farfli" ascii wide nocase
        $s3 = "trojan:win32/farfli" ascii wide nocase
        $s4 = "backdoor.farfli" ascii wide nocase
        $s5 = "farfli rat" ascii wide nocase
        $s6 = "backdoor.win32.farfli" ascii wide nocase
        $s7 = "win32/farfli" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Farfli (Rat) Execution & Triage
id: 726076c5-d117-5027-b4cd-8fa3681362d8
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Farfli malware family. Detects unauthorized persistence creation via Windows
  Registry Run keys, scheduled tasks, and privilege escalation indicative of RAT installations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/farfli
- 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.rat
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1055
- attack.t1571
- attack.t1056_001
- attack.t1113
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \reg.exe
    - \schtasks.exe
    - \cmd.exe
    - \powershell.exe
    CommandLine|contains:
    - \CurrentVersion\Run
    - /create /tn
    - bypass -enc
    - net user /add
    - net localgroup administrators
  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_FARFLI_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Farfli 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 = "farfli" 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 compromised endpoints showing anomalous process injections into explorer.exe or svchost.exe.
2. Deploy network intrusion rules matching Farfli custom 5-byte headers and beaconing patterns.
3. Revoke compromised Active Directory credentials and evaluate lateral movement paths.
4. Patch vulnerable office productivity suites against CVE-2012-0158 and CVE-2017-11882.

What to Avoid

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

1. Do not allow unmonitored TCP egress traffic over non-standard ports from core infrastructure.
2. Avoid relying solely on default Gh0st RAT signatures, as Farfli customizes packet headers.
3. Never execute untrusted Office email attachments containing legacy Equation Editor components.

References & External Analysis

• CISA Alert AA20-258A: Chinese Ministry of State Security-Affiliated Cyber Actors
• Trend Micro Security Intelligence: Farfli Remote Access Trojan Profile
• NIST National Vulnerability Database CVE-2017-11882
• CISA Advisory: AA20-258A
• Search "farfli" on VirusTotal (External Analysis)
• Search "farfli" on Any.Run (Sandbox Sandbox)
• Search "farfli" on MalwareBazaar (Malware Samples)

North American Authority Advisory (CISA / NIST)

The Cybersecurity and Infrastructure Security Agency (CISA) has published an official US federal advisory on this family, which can be mapped to NIST Cybersecurity Framework (CSF) incident response controls: AA20-258A ↗

Frequently Asked Questions

Related Threats (Category: Rat)

Explore other documented threats in the same operational category:

• Bandook
• Wabot
• Rescoms
• Turkojan
• Quasar
• Ghost
• Protux
• Plugx

Machine-readable

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