Microsoft Dusseldorf: Open-Source Out-of-Band Security Platform

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Meet Dusseldorf, Microsoft’s open-source out-of-band security platform.

Introduction to Dusseldorf

Out-of-band vulnerabilities arise when an application secretly communicates with an external system during an attack, requiring specialized infrastructure to monitor such activity. A recently released open-source project from Microsoft provides this infrastructure as a self-contained solution designed for private deployment.

Understanding Out-of-Band Vulnerabilities

Dusseldorf functions as an out-of-band application security testing platform, capturing network traffic across multiple protocols and enabling automated response generation for validation processes.

The Origin of the Name

The project’s name references Microsoft’s tradition of using geographic names for internal initiatives. The German city Düsseldorf inspired the name, with its abbreviation SSRF integrated into the project’s identity.

Key Features and Functionality

Detection Capabilities

The platform focuses on detecting defects that leave minimal traces within an application’s internal processes. These include server-side request forgery, cross-site scripting, server-side template injection, XML external entity flaws, and similar vulnerabilities.

Operational Mechanism

Detection relies on monitoring application behavior at the network perimeter, where Dusseldorf operates. Once implemented, the system runs DNS, HTTP, and HTTPS listeners tied to a domain such as *.yourdomain.net. All requests directed to this domain or its subdomains are logged.

Private Deployment Focus

The project refers to these subdomains as “zones,” meaning foo.yourdomain.net and foo.bar.yourdomain.net both fall under the same classification. Private deployment is the core design principle. Operators maintain control over identity integration, infrastructure size, active domains, and runtime policies governing request handling.

Deployment Options

Local Setup

Deployment requires a machine with one or more public IPv4 addresses and a domain whose name server records point to those addresses. The codebase is optimized for Azure and offers two deployment pathways. A local setup caters to lab environments and developer workflows, including credential generation, certificate configuration, and Docker Compose integration.

Azure Pathway

The Azure pathway manages cloud provisioning and database initialization via Helm. The setup process demands specific tools, including Docker, Docker Compose, Azure CLI, OpenSSL for TLS certificates, Python 3 with pip, the jq utility, and Helm.

Post-Deployment Interaction

Post-deployment, operators interact through a graphical interface and API, with command-line documentation available alongside these options. Dusseldorf is freely accessible on GitHub.

Conclusion

Dusseldorf addresses gaps in traditional security testing by focusing on indirect communication patterns. Its architecture emphasizes isolation, allowing organizations to tailor configurations to their specific network environments. By centralizing traffic monitoring and response mechanisms, Dusseldorf aims to streamline the identification and mitigation of out-of-band vulnerabilities.