MCP Defender is an innovative open-source desktop application that serves as an AI firewall, specifically designed to oversee and safeguard communications related to the Model Context Protocol (MCP). By functioning as a secure proxy between AI applications and MCP servers, it meticulously analyzes all communications in real-time to detect potential threats. This application automatically scans and secures all MCP tool calls, leveraging advanced LLM capabilities to identify malicious activities effectively. Users have the flexibility to manage the signatures utilized during the scanning process, enabling tailored security measures that fit their specific needs. MCP Defender excels in recognizing and preventing a range of AI security threats, such as prompt injection, credential theft, arbitrary code execution, and remote command injection. It seamlessly integrates with numerous AI applications, including Cursor, Claude, Visual Studio Code, and Windsurf, with plans for expanded compatibility in the future. The application provides intelligent threat detection and promptly alerts users as soon as it detects any malicious actions perpetrated by AI applications, ensuring a robust defense against evolving threats. Ultimately, MCP Defender empowers users with enhanced security and peace of mind in their AI interactions.