The Hunt for Tokens: When the Attack Surface Shifts to Session Credentials of Claude

The Anatomy of Token Theft in LLM Services

When a user interacts with an advanced assistant like Claude, the interface is not purely stateless: it relies on persistent session tokens, authentication cookies, and API keys that can be stored locally. The main factors that make these tokens vulnerable are:

1. Exposure in local configuration files – Many clients and IDEs save credentials in plaintext or with light encryption in directories like `~/.config`, `AppData`, or equivalent paths.

2. Unverified third-party extensions and tools – Plugins, editor extensions, and micro-agents based on MCP can access local storage. If compromised, they can exfiltrate tokens to command and control servers.

3. Persistence and abuse of quotas – A high-tier LLM token represents computational resources and economic credits. An attacker can use it to execute unauthorized workloads, scraping, or generate malicious code.

Lesson for the Siliceo Project: Rigorous State Management

In the Siliceo Project, we have addressed these risks from the early stages of design:

* No persistent tokens in plaintext – Session keys reside exclusively in protected memory areas or encrypted segments with hardware-derived keys.

* MCP perimeter validation – Every tool or extension that requires access to tokens is executed within a capability-based sandbox, preventing unauthorized access to files of other processes.

* Principle of least privilege – Credentials are generated with a limited duration and automatically revoked at the end of the session.

Practical Insight: How to Protect Your Credentials

Today

1. Audit configuration directories – Regularly check hidden directories (`~/.config`, `AppData`, etc.) to verify which tools have read access to token files.

2. Revocation and rotation – If you notice anomalous activity or sudden credit consumption, immediately revoke API keys and generate new credentials.

3. Client isolation – Run CLI or third-party agents with reduced privileges (non-root/admin) and separate browser sessions from development tool sessions. Applying these practices significantly reduces the attack surface related to session credentials and contributes to maintaining the integrity of LLM-based systems.