deploying-decoy-files-for-ransomware-detection

deploying-decoy-files-for-ransomware-detection is a skill for Claude Code from 26zl/cybersec-toolkit. It costs 87 tokens per session (1,723 once invoked), scanned A, original, MIT.

A guide to placing monitored decoy files on computers or file shares to detect ransomware activity. Ransomware is malware that encrypts files to disrupt access or demand payment.

In plain words
What is it for?
Use it to place canary documents in important directories, monitor file changes, send alerts through file-integrity tools or a SIEM, and test ransomware response procedures.
Why use it?
A ransomware process that changes a decoy file can trigger an early warning, including for variants that antivirus tools do not yet recognize. The decoys detect activity but do not prevent it.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Part of the cybersec-toolkit plugin — 197 skills, 2 hooks, 1 MCP server shipped together

Good fit Use it to place canary documents in important directories, monitor file changes, send alerts through file-integrity tools or a SIEM, and test ransomware response procedures.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/26zl/cybersec-toolkit/deploying-decoy-files-for-ransomware-detection
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add 26zl/cybersec-toolkit --skill deploying-decoy-files-for-ransomware-detection
Clone the repo
git clone --depth 1 https://github.com/26zl/cybersec-toolkit

Made for: Claude Code.

Or install cybersec-toolkit, the plugin that ships this one along with the rest of its 197 skills, 2 hooks, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

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README.md
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Your own site
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Your own site · 80×15
<a href="https://agentmods.dev/skills/26zl/cybersec-toolkit/deploying-decoy-files-for-ransomware-detection"><img src="https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/deploying-decoy-files-for-ransomware-detection.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 87 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,723 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00087 $0.01723
Opus 5 $0.00044 $0.00861
Sonnet 5 $0.00017 $0.00345
Haiku 4.5 $0.00009 $0.00172

Measured 8d ago against content hash 6220f2781356, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

deploying-decoy-files-for-ransomware-detection scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/agent.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/deploying-decoy-files-for-ransomware-detection/SKILL.md · 200 lines

How it starts

The opening of the file, as written. The whole thing — 200 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Deploying Decoy Files for Ransomware Detection

When to Use

  • Setting up early-warning detection for ransomware on file servers or endpoints
  • Supplementing EDR/AV with a deception-based detection layer that catches unknown ransomware variants
  • Creating high-fidelity ransomware alerts that have very low false-positive rates (legitimate users have no reason to touch decoy files)
  • Testing ransomware response procedures by validating that canary file modifications trigger the expected alerting pipeline
  • Protecting high-value file shares (finance, HR, legal) with tripwire files that indicate unauthorized encryption activity

Do not use decoy files as the sole ransomware defense. They are a detection mechanism, not a prevention mechanism, and should complement backups, EDR, and access controls.

Prerequisites

  • Python 3.8+ with watchdog library for cross-platform file system monitoring
  • Administrative access to target file shares or endpoints for canary placement
  • File integrity monitoring (FIM) tool or SIEM integration for alert routing
  • Understanding of target directory structure to place canaries in high-value locations
  • Windows: NTFS change journal or ReadDirectoryChangesW API access
  • Linux: inotify support in kernel (standard in modern kernels)

Workflow

Step 1: Design Canary File Strategy

Plan file placement for maximum detection coverage:

Canary File Placement Strategy:
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Naming Convention:
  - Use names that sort FIRST and LAST alphabetically in each directory
  - Ransomware typically enumerates directories A-Z or Z-A
  - Examples: _AAAA_budget_2024.docx, ~zzzz_report_final.xlsx

Placement Locations:
  - Root of every file share (\\server\share\_AAAA_canary.docx)
  - Desktop, Documents, Downloads on each endpoint
  - Department-specific shares (Finance, HR, Legal)
  - Backup staging directories
  - Home directories of high-privilege accounts

File Types:
  - .docx, .xlsx, .pdf (most targeted by ransomware)
  - .sql, .bak (database files, high value)
  - Mix of file types to detect ransomware that targets specific extensions

Read the full file on GitHub · 200 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 200 lines · 87 tokens per session scan A 6220f2781356

Subscribe to this mod's changes

deploying-decoy-files-for-ransomware-detection is a skill published in the GitHub repository 26zl/cybersec-toolkit (54 stars, last pushed yesterday), licensed MIT. It adds 87 tokens to every session and 1,723 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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