Strfry Nostr Spam Filter

A sophisticated spam filter for Strfry Nostr relays with reputation tracking, burst handling, and adaptive rate limiting.

Features

• Reputation-based filtering system with detailed logging
• Intelligent burst handling for follow lists
• Per-user and kind-specific rate limiting
• Content similarity detection
• New account protection
• Bot behavior detection
• Progressive penalty system
• Automatic recovery mechanism
• Configurable thresholds
• Memory-efficient cleanup system

Installation

1. Clone this repository:

git clone https://github.com/yourusername/strfry-spam-filter.git

2. Make the filter executable:

chmod +x relay-spam-filter.js

3. Configure your strfry relay to use the filter:

# Add to your strfry configuration
plugins = [
  {
    exec = "/path/to/relay-spam-filter.js"
  }
]

Configuration

Rate Limits and Burst Handling

// General rate limits
maxRepliesPerMinute: 50,
maxRepliesPerHour: 400,

// Kind-specific limits with burst handling
kindSpecificLimits: {
    0: { // Profile updates
        maxPerHour: 10,
        minTimeBetween: 300
    },
    1: { // Regular posts
        maxPerMinute: 30,
        maxPerHour: 200
    },
    3: { // Follow lists
        maxPerMinute: 120,
        maxPerHour: 360,
        minTimeBetween: 2,
        ignoreSimilarity: true,
        burstAllowance: {
            maxBurst: 500,       // Maximum events in burst
            burstWindow: 300,    // Window for burst (5 minutes)
            cooldownPeriod: 3600 // Cooldown after burst (1 hour)
        }
    },
    7: { // Reactions
        maxPerMinute: 60,
        maxPerHour: 300,
        ignoreSimilarity: true
    }
}

Reputation System

reputationConfig: {
    initialScore: 100,          // Starting reputation
    goodEventBonus: 1,          // Points for good events
    spamPenalty: -15,          // Base spam penalty
    recoveryRate: 3,           // Points/hour recovery
    minScore: -100,           // Minimum reputation
    maxScore: 1000,           // Maximum reputation
    blockThreshold: -50,      // Blocking threshold
    blockRecoveryThreshold: -25, // Recovery threshold
    
    // Progressive penalties
    penaltyScaling: {
        0: -15,    // Above 0 reputation
        "-25": -20, // Below -25
        "-50": -25  // Below -50
    },
    
    // Variable recovery rates
    recoveryScaling: {
        0: 3,      // Above 0
        "-25": 2,  // Below -25
        "-50": 1   // Below -50
    }
}

New User Protection

newPubkeyReplyThreshold: 60,    // Seconds before first reply
newPubkeyMaxPostsIn5Min: 10     // Initial rate limit

How It Works

Enhanced Reputation System

The filter maintains a detailed reputation score for each user:

• New users start at 100 points
• Good behavior increases reputation gradually
• Spam behavior triggers scaled penalties based on current reputation
• Recovery rates vary by reputation level
• Detailed logging of all reputation changes
• Special handling for follow list operations

Burst Handling

Special consideration for bulk operations:

• Follow list updates (kind 3) can operate in burst mode
• Up to 500 follows in a 5-minute window
• Cooldown period after burst completion
• Normal rate limits apply during cooldown
• Reputation affects burst allowances

Spam Detection

Multiple detection mechanisms:

• Adaptive Rate Limiting

  • Per-user and per-kind limits
  • Reputation-based scaling
  • Burst mode for specific operations

• Content Analysis

  • Cross-user content similarity
  • Fast reply detection
  • Bot pattern recognition

• New Account Protection

  • Progressive rate limits
  • Reply waiting periods
  • Initial posting restrictions

Logging and Monitoring

Comprehensive logging system:

[2024-12-19T10:15:30.123Z] Event abc123 from pubkey xyz789 (reputation: 85.50)
[2024-12-19T10:15:30.124Z] Reputation update: 85.50 -> 86.50 (change: +1.00)
[2024-12-19T10:15:30.125Z] Burst tracking - count: 42/500 (window: 300s remaining)

Memory Management

Efficient resource usage:

• Periodic cleanup of old data
• Configurable retention periods
• Automatic purging of inactive users
• Memory-efficient data structures
• Burst tracking cleanup

Contributing

Contributions are welcome!

License

MIT License - See LICENSE file for details