Pynamer

Overview

Pynamer (cataloged across security vendors and threat intelligence databases under signatures including Trojan:Win32/Pynamer, Trojan.Pynamer, and Trojan:Win32/Pynamer!ac) is a versatile family of compiled Python trojans active since 2018. Packaged into standalone Windows Portable Executables using utilities like PyInstaller, cx_Freeze, or Py2exe, Pynamer encapsulates complete Python runtime environments and obfuscated bytecode to evade conventional static antivirus signatures. In the wild, Pynamer is distributed via malicious cracked software installers, game cheat tools, and malicious email attachments. Upon execution, the malware extracts its internal Python payload into %Temp%, establishes persistent autostart registry entries under Windows CurrentVersion\Run, and initiates encrypted C2 communications. Pynamer acts as an initial access stager, capable of capturing keystrokes, harvesting browser credentials, downloading secondary malicious payloads, and providing interactive backdoor shells.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Pynamer
• Trojan.Pynamer
• Trojan:Win32/Pynamer!ac
• Win32/Pynamer

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: Python-Based Information Stealers

Known Derivatives & Downstream Variants: Pynamer.A · Pynamer.Ac

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:

• T1059.006: Restrict execution of scripting languages such as PowerShell, VBScript, or Python to authorized administrators. Enforce Script Block Logging.
• T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.

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.

• 1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e
• 2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f

Delivery vectors

• cheat_installer.exe
• pynamer_setup.exe

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\PythonUpdater
• %Temp%\_MEI\pynamer_core.exe

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_PYNAMER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Pynamer"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "pynamer" ascii wide nocase
        $s2 = "trojan:win32/pynamer" ascii wide nocase
        $s3 = "trojan.pynamer" ascii wide nocase
        $s4 = "trojan:win32/pynamer!ac" ascii wide nocase
        $s5 = "win32/pynamer" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Pynamer (Trojan) Execution & Triage
id: ae55771e-7877-57be-a7ef-4f57f7e67126
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Pynamer 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/pynamer
- 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.t1027
- attack.t1059_006
- attack.t1547_001
- attack.t1105
- attack.t1555_003
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_PYNAMER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Pynamer 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 = "pynamer" 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. Quarantine the endpoint to halt the execution of the unpacked Python payload, which could be an infostealer or ransomware.
2. Clear the Windows `%Temp%` directory, specifically looking for and deleting any `_MEIxxxxxx` folders created by the PyInstaller stub.
3. Submit the original massive executable to a malware analyst for unpacking and decompilation to understand the specific threat.
4. Perform a full system sweep to determine the initial delivery vector (e.g., a phishing email or a compromised download).

What to Avoid

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

1. Do not waste time trying to statically analyze the original `.exe` file using standard dissassemblers; you must unpack the Python bytecode first.
2. Avoid assuming the threat is contained just by deleting the `.exe`; the script may have already executed and established persistence elsewhere.

References & External Analysis

• Microsoft Defender Security Intelligence - Trojan:Win32/Pynamer
• Trend Micro Threat Encyclopedia - Trojan.Win32.Pynamer
• Search "pynamer" on VirusTotal (External Analysis)
• Search "pynamer" on Any.Run (Sandbox Sandbox)
• Search "pynamer" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Winevar
• Murofet
• Luminorat
• 2345Explorer
• Dnschange
• Dostre
• Cidox
• Perfectoptimizer

Machine-readable

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