Pyme
Table of Contents
Overview
Executive Summary
Pyme is a malicious program that exhibits characteristics of both a Trojan and a Worm. It is designed to covertly infiltrate Windows systems, establish a persistent backdoor, and then aggressively attempt to propagate itself across local networks or via removable media, creating a disruptive and potentially widespread security incident.Infection Vector and Technical Capabilities
Pyme often infiltrates networks initially through malicious email attachments or when a user connects an already infected USB drive to a corporate workstation. Upon execution, Pyme focuses on persistence and propagation:- Worm-like Propagation: Pyme actively scans the local subnet for open, unauthenticated file shares (SMB) or exploits legacy vulnerabilities to copy its executable laterally. It will also aggressively infect any connected removable media (USB drives), hiding legitimate files and replacing them with malicious shortcuts to facilitate further spread.
- System Modification and Persistence: To ensure it runs every time the system boots, Pyme modifies the Windows Registry (e.g., adding entries to `HKCU\Software\Microsoft\Windows\CurrentVersion\Run`). It may also disable built-in security features like Windows Defender or the Task Manager to protect itself from termination.
- Backdoor Functionality: While spreading, Pyme often opens a covert backdoor, allowing remote attackers to issue commands, download secondary malware, or exfiltrate basic system data.
Threat Assessment
A Pyme infection is highly disruptive. Its worm-like propagation capabilities can rapidly saturate a local network, causing significant downtime and overwhelming IT helpdesks. The backdoor functionality also presents a serious risk of data theft or the deployment of secondary, more destructive payloads like ransomware.Incident Response and Remediation
- Immediate Network Segmentation: Isolate infected subnets immediately to halt the worm's lateral movement and prevent the infection of mapped network drives.
- Comprehensive Antivirus Sweep: Deploy an enterprise-grade anti-malware solution across the affected subnets to identify, quarantine, and remove the Pyme executable and its associated registry keys.
- Removable Media Policy Review: Pyme's reliance on USB propagation strongly suggests that the organization's policies regarding removable media are either lacking or unenforced. Consider disabling USB storage access via Group Policy to prevent future outbreaks.
Known aliases
Threat reports may refer to this family under multiple names:
MITRE ATT&CK Techniques
Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:
| Technique | Name | Tactic | Official Spec |
|---|---|---|---|
T1059 | Command and Scripting Interpreter | Execution | ATT&CK ↗ |
T1091 | Replication Through Removable Media (The core propagation mechanism using autorun.inf) | Lateral Movement | ATT&CK ↗ |
T1547.001 | Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder | Persistence | ATT&CK ↗ |
T1562.001 | Impair Defenses: Disable or Modify Tools | Defense Evasion | ATT&CK ↗ |
Tactical Mitigations
Based on the techniques used by this family, consider the following defensive strategies:
- T1059: 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):
| D3FEND ID | Countermeasure Name | Tactic | Countered ATT&CK | Defensive Guidance |
|---|---|---|---|---|
D3-SEA | Script Execution Analysis | Detect | T1059 | Analyze script block syntax and command arguments at runtime to detect malicious automation. |
D3-RMC | Removable Media Access Control | Harden | T1091 | Enforce Group Policy settings disabling Windows autorun and block execution permissions on removable USB storage media. |
D3-RPM | Registry Persistence Monitoring | Detect | T1547.001 | Audit and restrict write privileges to user and machine-level Registry Run/RunOnce keys using Endpoint Privilege Management. |
D3-STA | Security Tool Anti-Tamper Enforcement | Harden | T1562.001 | Block unauthorized modification of antivirus registry flags and prevent stopping security agent services. |
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:
Tier 1 Primitive Artifact Rule (Fast Triage)
Matches raw strings and file markers. Vulnerable to binary repacking and simple obfuscation.
rule MALWARE_WIN_PYME_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Pyme"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "pyme" ascii wide nocase
$s2 = "worm.pyme" ascii wide nocase
$s3 = "trojan.pyme" ascii wide nocase
$s4 = "win32/pyme" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Tier 2 Behavioral Context Rule (Process Chains & Sigma)
Tracks parent-child process anomalies and suspicious scripting telemetry. Resilient against file renames.
title: SystemHelpDesk Detection - Pyme (Ransomware) Execution & Triage
id: 4aa84550-254a-572b-a56b-1b800849f6d4
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Pyme 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/pyme
- 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.t1059
- attack.t1091
- attack.t1547_001
- attack.t1562_001
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: criticalTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_PYME_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Pyme 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 = "pyme" 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.
- Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Pyme from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.
- Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Pyme symmetric encryption keys or uncompiled payload components may still reside in memory.
- 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 Pyme to inhibit recovery.
- 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.
- Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Pyme 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.
- Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Pyme.
- Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.
- Do not connect clean backup drives or external storage to the affected network until Pyme eradication is completely verified.
References & External Analysis
- Search "pyme" on VirusTotal (External Analysis)
- Search "pyme" on Any.Run (Sandbox Sandbox)
- Search "pyme" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Pyme and what threat category does it belong to?
Pyme is classified as a Ransomware. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments.
How does Pyme establish persistence and evade defensive controls?
Pyme typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks.
What are the essential incident response steps for mitigating a Pyme compromise?
Security teams responding to Pyme should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups.
What cryptographic algorithms and file targeting techniques does Worm.Pyme employ during execution?
Worm.Pyme typically leverages hybrid cryptographic architectures combining symmetric stream or block ciphers (such as AES-256 or ChaCha20) for rapid file encryption with asymmetric algorithms (such as RSA-2048 or Curve25519) to securely protect the session keys. It aggressively targets sensitive file extensions including corporate documents, databases, virtual disks, and backups while systematically executing commands to delete Volume Shadow Copies (vssadmin delete shadows /all /quiet) and disable system recovery options.
Are decryptors available for Worm.Pyme, and what is the recommended recovery procedure?
Decryption availability for Worm.Pyme depends on whether security researchers or law enforcement (such as the No More Ransom initiative) have recovered the master private keys or discovered flaws in its key generation routines. Victims should never pay the extortion demand, as payment fuels criminal operations without guaranteeing file restoration. The recommended recovery procedure entails isolating infected hosts, conducting forensic disk imaging, identifying the root access vector, and restoring validated systems from immutable offline backups.
How do I remove the Pyme Ransomware from Windows?
Manual removal of Pyme is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
Is Pyme a virus or a Ransomware?
Pyme is classified as a Ransomware. Unlike traditional viruses that infect files, modern malware like Pyme typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Pyme infection?
Symptoms of Pyme can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Protect Your Network Against Ransomwares
Want to prevent Pyme and similar threats from compromising your organization? Read our comprehensive defensive guide: Ransomware Containment & Incident Response.
📣 Threat Intel Correction or Update?
Notice an outdated IOC, unlisted alias, or disputed attribution? Threat researchers are invited to propose an update on GitHub or contact the SystemHelpDesk research desk. All community revisions are credited in our public CHANGELOG.
Machine-readable
Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/pyme.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.