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Overwatch

Overwatch is a runtime security proxy for MCP (Model Context Protocol) servers. It intercepts tool calls, detects Tool Shadowing attacks (CVE-2025-6514), and enforces policies before execution.

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Why Overwatch?

AI agents using MCP servers have access to powerful tools - databases, filesystems, and APIs. Without access control:
  • A single prompt injection can drop database tables
  • Malicious MCP servers can shadow trusted tools
  • Dangerous operations execute without human review
  • No audit trail of what the AI agent did
Overwatch adds a security layer between AI agents and these dangerous operations.

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Quick Start

# Install
npm install -g @dotsetlabs/overwatch

# Wrap any MCP server
overwatch wrap npx @modelcontextprotocol/server-postgres

# Or start with configuration
overwatch init
overwatch start

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Key Features

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Tool Shadowing Detection

Detects CVE-2025-6514 where malicious MCP servers impersonate trusted tools:
  • Schema hashing - SHA-256 fingerprints of tool definitions
  • Collision detection - Same tool name across multiple servers
  • Mutation monitoring - Schema changes mid-session
  • Description analysis - 30+ suspicious patterns

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Policy Engine

Configure fine-grained access control: 
version: 1
servers:
  postgres:
    command: npx
    args: ["-y", "@modelcontextprotocol/server-postgres"]
    policies:
      - tools: ["query", "select"]
        action: allow
      - tools: ["insert", "update"]
        action: prompt
      - tools: ["drop_*", "delete_*"]
        action: deny

toolShadowing:
  enabled: true
  checkDescriptions: true
  detectMutations: true

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Session Grants

After approving an operation, grant temporary permissions:
GrantDurationUse Case
OnceSingle useOne-time operations
5 min5 minutesShort tasks
15 min15 minutesModerate tasks
Session24 hoursFull development session
Sessions can be revoked at any time with overwatch sessions revoke.

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Audit Logging

Complete audit trail of all operations: 
overwatch logs                    # View recent logs
overwatch logs --tail             # Follow in real-time
overwatch logs --export json      # Export for analysis
overwatch stats                   # View statistics
Supports JSON, CSV, and CEF (Common Event Format) for SIEM integration.

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Reliability Features

  • Circuit breaker - Protects against upstream failures
  • Request timeouts - Prevents hanging operations
  • Connection recovery - Exponential backoff reconnection
  • Fail modes - Configure behavior when upstream fails

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Architecture

AI Client → MCPProxy → ToolShadowingDetector → PolicyEngine
                ↓              ↓                    ↓
           AuditLogger    CircuitBreaker      SessionManager
                ↓
           MCP Server

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Next Steps

Installation

Install Overwatch

Wrap Command

Protect any MCP server

Tool Shadowing

Understand tool shadowing detection