Software-defined perimeter (SDP): What is it and what are the benefits?

A software-defined perimeter is a security framework that prevents outsiders from eavesdropping on your router and server infrastructure. It acts as a cloak of invisibility, hiding your internet-connected infrastructure from unauthorized users.

Developed by the Cloud Security Alliance in 2013, SDP bases the network perimeter on software rather than hardware, and dynamically controls user access to network resources. SDP ensures that only authorized users and devices can establish connections to specific resources.

A software-defined perimeter solution forms a virtual boundary around your company’s assets at the network layer, instead of the application layer. By reducing the risk to endpoints that connect from anywhere, SDP allows your company’s employees to securely access the resources they need, whether they work on site or remotely.

An SDP authenticates a user and their device and then establishes a connection between that device and the company’s servers. This means that an employee is connected to their own network and can only access certain resources, instead of having broad access to a larger company-wide network. Even if cybercriminals steal the user’s account, they can only access limited resources.

The SDP security framework integrates these key concepts, principles, and processes:

• User and device verification. Every user and device undergoes two checks — pre-authentication verifies the user’s identity and trustworthiness of the device, and pre-authorization determines what resources the user should be allowed to access.
• Establishing the SDP components. For an SDP to work, IT administrators must deploy and configure the key SDP components — the client device, the controller, and the gateway. The client device is the endpoint which the user uses to access the network resource, the controller acts as the central coordinator and is responsible for user authentication, while the gateway enforces access control and establishes connections between users/devices and the network resources.
• Establishing secure network connections. If the pre-authentication and pre-authorization is successful, the gateway establishes secure network connections between users/devices and the specific resources. Encrypted connections ensure that the data remains secure during transit.
• Dynamic firewalls. SDP typically uses firewalls to enhance security. With access policies adapting based on changing conditions, dynamic firewalls can restrict or allow traffic in real-time, preventing unauthorized users from accessing the resources.
• Zero trust network access. SDP is based on the zero trust security model in which no user is considered trustworthy by default. Users and devices must undergo strict authorization and identity verification to access internal resources, regardless of whether they are situated inside or outside the network perimeter.
• Continuous monitoring. The SDP system continually monitors user and device behavior and network conditions. It automatically revokes or restricts access if it detects any changes or anomalies.

The three key components of the software-defined perimeter are the client device, SDP controller, and SDP gateway. Let’s look at them in more detail.

A client device is an endpoint that requires access to protected resources. A client device can be the user’s laptop, smartphone, or tablet. This device must authenticate itself and prove its legitimacy before gaining access to the resources it requires. These devices must have an SDP client software installed to facilitate the authentication and secure communication with the SDP system.

An SDP controller is the brain of the SDP architecture. It verifies user identity and authenticates the client devices to determine which of them should be allowed to connect. Once the user and their device has been authenticated, the controller approves of the user and their device, and sends its approval to the SDP gateway. It also provides the client device with a unique, temporary access information for it to connect to protected applications and data.

An SDP gateway is the gatekeeper to the protected resources. It ensures that only authenticated client devices can access them. The gateway checks the controller-issued credentials of client devices and establishes a secure connection between the client and the destination resource.

Software defined perimeter offers four deployment models to satisfy the needs of different organizations. In the client-to-gateway (C2G) model, clients use SDP software to connect to an SDP gateway, which provides access to protected resources. Remote employees and external partners use this model to connect to a company’s internal network resources. In theclient-to-server (C2S) model, SDP software directly communicates with the server hosting the resources, while in the server-to-server (S2S) model, server endpoints communicate with each other via the SDP, ensuring secure inter-server connections. In the gateway-to-gateway (G2G)model, SDP gateways communicate with each other. This last model can be used, for example, when branch offices need to communicate with a central office.

SDP offers three main infrastructure models — cloud-based, on-premise, and hybrid. In acloud-based model, the SDP infrastructure is hosted in a cloud by a third-party, which is ideal for businesses that largely use cloud infrastructure. In an on-premise model, all SDP components are hosted within the organization’s own data center and facilities, giving businesses complete control of the SDP infrastructure. The hybrid model combines elements of both cloud-based and on-premise models, hosting some components on site and others in the cloud.

The flexibility of SDP deployment makes it adaptable for a variety of applications. SDP provides a secure access to remote employees, ensures a secure access to cloud resources, protects the communication between IoT devices and backend systems, and offers secure ways to provide partners and vendors with access to certain parts of the network without exposing the whole system.

The three main benefits of software defined perimeter are its scalability, security, and easy management. Let’s examine them one by one.

SDP architecture is inherently flexible, so organizations can easily scale their network resources up and down based on demand, without major infrastructural changes. They can purchase an SDP as a service and add as many users to their network as they need. SDP is especially beneficial for businesses that are experiencing growth.

An SDP enforces a “zero trust” approach and creates individualized perimeters for every single user, ensuring endpoint protection, secure network connections, application security, and more. Even if an employee is working from a beach on a Caribbean island, they will still be protected and can access everything they need.

Since an SDP is a software solution, it can be easily managed from a central location. Adding new users, changing their privileges, and managing a company’s network is easy and doesn’t take much time.

Software-defined perimeter plays a key role in zero trust architecture by ensuring that network access is only granted to authorized devices and users, as opposed to the traditional network security approach of trusting anyone inside the network. SDP authenticates every access request and ensures that only validated users and devices can connect, regardless of their location. This upholds the zero trust principle “Never trust, always verify.”

SDP is among the most advanced network security solutions together with VPNs. However, these security tools have a different approach to network access. A VPN grants access to a broader network segment, often relying on a perimeter-based trust model, while an SDP is based on zero trust architecture, offering identity-based access to specific resources. If you’re interested to find out more, check out our article on SDP vs. VPN.