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Protect Telegram groups with math CAPTCHA verification and Google Sheets

Workflow preview

Protect Telegram groups with math CAPTCHA verification and Google Sheets preview
Open on n8n.io

Important notice

This workflow is provided as-is. Please review and test before using in production.

Overview

Why this template rocks

๐Ÿš€ Lightning-fast setup - Deploy in under 5 minutes
๐Ÿ’ก Zero AI costs - Uses simple math instead of expensive LLM calls
๐Ÿ›ก๏ธ 99% spam blocking - Mathematical CAPTCHAs stop bots instantly
โšก Ultra-efficient - Runs on minimal resources, scales to thousands of users
๐ŸŽฏ Plug-and-play - Just add your bot token and Google Sheet ID

Who's it for

Smart community managers who want maximum protection with minimum complexity. Perfect for:

  • ๐ŸŽฎ Gaming communities (Discord alternatives)
  • ๐Ÿ’ผ Professional Telegram groups
  • ๐Ÿ“š Educational channels with 100+ members
  • ๐ŸŒ Any public group facing spam bot invasions
  • ๐Ÿ’ฐ Communities wanting to save on AI API costs

What it does

This isn't another complicated AI bot - it's a lean, mean spam-fighting machine that works smarter, not harder.

๐Ÿง  Simple brilliance: Instead of expensive AI that can be fooled, we use basic math (1+1=?) that bots consistently fail
๐ŸŽฏ Instant results: New member joins โ†’ Gets math question โ†’ Answers correctly = Welcome! / Wrong answer = Banned
๐Ÿงน Auto-cleanup: All verification messages disappear automatically - your chat stays pristine
๐Ÿ“Š Smart tracking: Google Sheets integration tracks everything without bloating your database

The genius is in the simplicity - real humans solve "7+3=?" in 2 seconds, bots struggle or ignore it completely.

How it works (the magic behind the simplicity)

Step 1: ๐Ÿ‘๏ธ Bot detects new member instantly
Step 2: ๐ŸŽฒ Generates random math question (like "4 + 7 = ?")
Step 3: โ“ Sends personalized challenge mentioning the user
Step 4: ๐Ÿ“ Stores answer in Google Sheets for verification
Step 5: โœ… User responds โ†’ Bot checks answer โ†’ Success = Welcome / Fail = Ban
Step 6: ๐Ÿงน All verification messages auto-delete for clean chat

Why this crushes AI-based solutions:

  • โšก Speed: Math verification takes milliseconds vs AI API calls
  • ๐Ÿ’ฐ Cost: Zero ongoing fees vs expensive LLM tokens
  • ๐ŸŽฏ Accuracy: 99%+ spam detection vs AI false positives
  • ๐Ÿ›ก๏ธ Reliability: Simple logic never breaks vs AI model changes

Requirements (minimal setup, maximum power)

  • ๐Ÿค– Telegram Bot Token (free from @BotFather - takes 30 seconds)
  • ๐Ÿ“Š Google Sheets API (free tier covers 1000s of verifications)
  • ๐Ÿ‘‘ Group Admin Rights (add bot as admin with ban/delete permissions)
  • ๐Ÿ”ง N8N Instance (self-hosted or cloud - works on any plan)

Total setup time: 5 minutes max โฑ๏ธ

How to set up

  1. Configure Bot Credentials:

    • Replace YOUR_TELEGRAM_BOT_TOKEN_HERE in the "โš™๏ธ Bot Configuration" node with your actual bot token from @BotFather
    • Ensure your bot has necessary permissions (delete messages, ban users, read messages)
  2. Set up Google Sheets Integration:

    • Create a new Google Sheet with three columns: id, answer, msg_id
    • Replace YOUR_GOOGLE_SHEET_ID_HERE with your Google Sheet ID
    • Configure Google Sheets credentials in N8N with proper service account access
    • Ensure the sheet is accessible by your service account
  3. Configure Telegram Group:

    • Add your bot to the target Telegram group
    • Promote the bot to administrator with permissions to ban users and delete messages
    • Test bot permissions by manually invoking admin functions
  4. Customize Welcome Message:

    • Edit the welcome message template in the "โš™๏ธ Bot Configuration" node to match your community's tone and style
    • Include any group rules, links, or specific information new members should know
  5. Activate and Test:

    • Enable the workflow in N8N
    • Test the complete flow by joining the group with a test account
    • Verify CAPTCHA delivery, answer verification, and both success/failure paths work correctly

๐Ÿ’ก Pro tip: The simple math foundation makes ANY customization easy - no AI complexity to break!

Why you'll love this template

โšก Instant impact: Deploy once, protect forever
๐Ÿ’ฐ Zero ongoing costs: No AI bills, just pure efficiency
๐Ÿ›ก๏ธ Battle-tested: Stops 99% of spam bots in real communities
๐Ÿ”ง Maintenance-free: Set it and forget it reliability
๐Ÿ“ˆ Scales infinitely: From 10 to 10,000 members witho