What it does. Deploys and monitors ransomware canary files using Python's watchdog library, placing decoy files mimicking high-value targets (financial records, credentials, database exports) where ransomware enumerates first, and alerting via email, Slack, or syslog on any read/modify/rename/delete. Use for early-warning ransomware detection on file servers, NAS, or endpoints, or to supplement EDR where agents can't be deployed. Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).

Install

• npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill deploying-ransomware-canary-files, or copy the skill folder into ~/.claude/skills/deploying-ransomware-canary-files/.
• Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/deploying-ransomware-canary-files/SKILL.md

SKILL.md (verbatim)

name: deploying-ransomware-canary-files
description: Deploys and monitors ransomware canary files using Python's watchdog library, placing decoy files mimicking high-value targets (financial records, credentials, database exports) where ransomware enumerates first, and alerting via email, Slack, or syslog on any read/modify/rename/delete. Use for early-warning ransomware detection on file servers, NAS, or endpoints, or to supplement EDR where agents can't be deployed.
domain: cybersecurity
subdomain: ransomware-defense
tags:
- ransomware
- canary-files
- watchdog
- detection
- early-warning
- deception
- defense
version: 1.0.0
author: mahipal
license: Apache-2.0
nist_csf:
- PR.DS-11
- RS.MA-01
- RC.RP-01
- PR.IR-01
mitre_attack:
- T1486
- T1083
- T1490
- T1485
mitre_f3:
  version: '1.1'
  tactics:
  - monetization
  techniques:
  - id: F1018
    name: Convert to Cryptocurrency
    tactic: monetization
    source: f3
  - id: F1017
    name: Conversion to Physical Monetary Instruments
    tactic: monetization
    source: f3
  - id: F1025.003
    name: 'Electronic Funds Transfer: Wire Transfer'
    tactic: monetization
    source: f3

Deploying Ransomware Canary Files

When to Use

• Deploying proactive ransomware detection on file servers, NAS devices, or endpoint systems
• Building an early-warning system that detects ransomware before it encrypts business-critical data
• Supplementing EDR solutions with lightweight canary file monitoring on systems where agents cannot be deployed
• Testing ransomware incident response procedures by simulating canary file triggers
• Monitoring shared drives, home directories, and backup volumes for unauthorized file operations

Do not use as a replacement for endpoint protection, backup strategy, or network segmentation. Canary files are a detection layer, not a prevention mechanism.

Prerequisites

• Python 3.8+ with pip
• watchdog library (pip install watchdog)
• Write access to directories where canary files will be placed
• SMTP server credentials or Slack webhook URL for alerting
• Administrative access for placing canaries in system directories

Workflow

Step 1: Generate Canary Files

Create decoy files with realistic names and content that attract ransomware scanners. Files should have names like Passwords.xlsx, Financial_Report_2026.docx, backup_credentials.csv and contain plausible-looking but fake data. Place them in directories ransomware typically targets first: user desktops, Documents folders, network share roots, and backup paths.

Step 2: Deploy Filesystem Monitor

Use Python's watchdog library with a custom FileSystemEventHandler that watches canary file paths. The handler triggers on on_modified, on_deleted, on_moved, and on_created events for canary files. Any legitimate user or process should never touch these files, so any interaction is a high-confidence indicator of ransomware or unauthorized access.

Step 3: Configure Alert Pipeline

Wire the filesystem monitor to multiple alert channels: email via SMTP, Slack webhook POST, syslog forwarding to SIEM, and local log file. Include the triggering event type, file path, timestamp, and process information (when available) in alert payloads.

Step 4: Validate and Test

Simulate ransomware behavior by programmatically modifying, renaming, and deleting canary files to verify the detection pipeline fires correctly. Measure time-to-alert and validate alert delivery across all configured channels.

Key Concepts

Tools & Systems

• watchdog: Python filesystem monitoring library using OS-native event APIs
• smtplib: Python standard library for SMTP email alerting
• requests: HTTP library for Slack webhook integration
• hashlib: SHA-256 hashing for canary file integrity verification
• psutil: Process information gathering when canary file access is detected

Output Format

RANSOMWARE CANARY ALERT
========================
Timestamp: 2026-03-11T14:23:07Z
Event: FILE_MODIFIED
Canary File: /srv/shares/finance/Passwords.xlsx
Directory: /srv/shares/finance
SHA-256 Before: a3f2...8b4c
SHA-256 After: 7e91...2d3f
Alert Channels: [email, slack, syslog]
Action: Investigate immediately - potential ransomware activity

Other files in this skill

• LICENSE
• references/api-reference.md
• scripts/agent.py

references/api-reference.md (verbatim)

API Reference: Deploying Ransomware Canary Files

Canary File Deployment

Monitoring Functions

CanaryFileHandler Events

Alert Channels

Ransomware Extension Detection

CLI Usage

# Deploy canary files
python agent.py --action deploy --dirs /srv/shares /home/admin/Documents

# Monitor canary files with Slack alerts
python agent.py --action monitor --slack-webhook https://hooks.slack.com/...

# Verify canary file integrity
python agent.py --action verify

# Test detection pipeline
python agent.py --action test

Python Libraries

References

• Elastic Security Labs: Ransomware Canary Files: https://www.elastic.co/security-labs/ransomware-in-the-honeypot-how-we-capture-keys
• Huntress Ransomware Canaries: https://support.huntress.io/hc/en-us/articles/4404005167763
• Python Watchdog Documentation: https://python-watchdog.readthedocs.io/
• CISA #StopRansomware Guide: https://www.cisa.gov/stopransomware/ransomware-guide

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