Pycrypter

Overview

Executive Summary

Infection Vector and Technical Capabilities

• Standalone Execution: The malware is usually packaged as a bulky `.exe` file. When run, it extracts a temporary Python interpreter and the malicious `.py` scripts into the `%Temp%` directory to execute.
• Cryptographic Implementation: PyCrypter typically utilizes well-known Python cryptography libraries (like `cryptography` or `PyCryptodome`) to implement strong encryption (e.g., AES-256 for files, secured by an RSA public key).
• Volume Shadow Copy Deletion: The Python script will utilize the `os.system` or `subprocess` modules to execute native Windows commands (like `vssadmin delete shadows`) to destroy local backups before encryption begins.

Threat Assessment

Incident Response and Remediation

• Immediate Network Severance: Isolate the infected endpoint (and any servers it can reach) from the network to halt the spread of the encryption across mapped drives.
• Reverse Engineering Potential: Because it is written in Python, incident responders may occasionally be able to decompile the executable (using tools like `uncompyle6`) to recover the source code. In rare cases of poor cryptographic implementation, this might reveal a hardcoded key or a flaw allowing for decryption.
• Restore from Offline Backups: Paying the ransom is strongly discouraged. Eradication requires a complete bare-metal wipe of the infected infrastructure and a full restoration from secure, offline backups.

Known aliases

Threat reports may refer to this family under multiple names:

• Ransom.PyCrypter
• Python.Ransomware
• Win32/Filecoder.Python

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.

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_PYCRYPTER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Pycrypter"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "pycrypter" ascii wide nocase
        $s2 = "ransom.pycrypter" ascii wide nocase
        $s3 = "python.ransomware" ascii wide nocase
        $s4 = "win32/filecoder.python" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Pycrypter (Ransomware) Execution & Triage
id: f83d2d68-5a4e-5e03-a2d0-0a6879e312c3
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Pycrypter 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/pycrypter
- 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.t1486
- attack.t1490
- attack.t1059_006
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: critical

rule MALWARE_WIN_PYCRYPTER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Pycrypter 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 = "pycrypter" 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. Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Pycrypter from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.
2. Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Pycrypter symmetric encryption keys or uncompiled payload components may still reside in memory.
3. Audit process execution logs and terminate active scripting interpreters (e.g. PowerShell, CMD, WScript) or commands executing 'vssadmin.exe delete shadows' or 'wbadmin' used by Pycrypter to inhibit recovery.
4. Investigate the initial compromise vector (such as exposed RDP instances, spearphishing attachments, or vulnerable edge gateways) and enforce an immediate credential reset for all compromised Active Directory accounts.
5. Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Pycrypter binary and related persistence hooks are eradicated.

What to Avoid

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

1. Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Pycrypter.
2. Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.
3. Do not connect clean backup drives or external storage to the affected network until Pycrypter eradication is completely verified.

References & External Analysis

• Search "pycrypter" on VirusTotal (External Analysis)
• Search "pycrypter" on Any.Run (Sandbox Sandbox)
• Search "pycrypter" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Krament
• Psexec
• Whimoo
• Trialkiller
• Fdoh
• Bitrepeyp
• Insebro
• Shepher

Machine-readable

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