MCP Security Risk Analysis and Protection Practices

With the rapid development of the Model Context Protocol (MCP), its security issues have become increasingly prominent. Currently, the MCP ecosystem is still in its infancy, and various potential attack methods continue to emerge, making it difficult for existing protocols and tools to effectively defend against them. To enhance the security of MCP, some security teams have developed specialized testing tools to help identify security vulnerabilities in product design through practical attack drills.

This article will introduce several common attack methods in the MCP system, including information poisoning, hidden malicious instructions, etc., and provide corresponding protection suggestions.

Common Attack Techniques

1. Web Content Poisoning

Attackers can embed malicious prompts in seemingly normal web pages, which will trigger unexpected actions when the large model client accesses them. There are mainly two methods:

• Comment-based poisoning: Inserting malicious keywords into HTML comments
• Encoding-based poisoning: Encoding malicious prompts to hide them, making them harder to detect.

2. Third-party interface pollution

When MCP calls a third-party API and directly returns data, an attacker can inject malicious content into the returned JSON and other data.

3. Malicious Function Override

By defining a malicious function with the same name as the original function, induce the large model to call the malicious version preferentially.

4. Add global check logic

A malicious check function must be executed before all tools run as required in the prompt.

Techniques for Hiding Malicious Prompts

• Use large model-friendly encoding methods, such as Hex Byte, NCR encoding, etc.
• Randomly return content with malicious payloads, increasing detection difficulty

Protection Recommendations

1. Strengthen the filtering and validation of external inputs
2. Avoid directly returning unprocessed third-party API data
3. Establish strict naming and calling conventions for functions
4. Handle global logic injection with caution
5. Parse and perform security checks on the encoded content.
6. Implement dynamic security scanning and monitor for abnormal behavior.

The security construction of the MCP ecosystem has a long way to go. Both developers and users should remain vigilant, strictly control every link, and jointly build a safe and reliable MCP environment.