SDP vs. VPN: software-defined perimeter explained

SDP vs. VPN showcases the differences between the two solutions aimed at safeguarding remote workers. Software-defined perimeter (SDP) emerged as one of the top contenders for the most secure remote network access method. For years, VPN solutions have dominated this field.

In this article, we will look closer at what an SDP is, where it comes from, and how it works. Then, it will be easy to contrast SDP vs. VPN and understand their differences.

What is a software-defined perimeter (SDP)?

A software-defined perimeter (SDP) is a security technique forming a virtual network boundary. As this boundary obscures the network from outsiders, SDP has also gained the name "black cloud."

SDP controls access to internal resources based on the identity of the users. This way, it removes many security risks, diminishing the potential attack surface of the company infrastructure.

Software-defined perimeter gains this name because it creates a restricted perimeter maintained by software applications rather than hardware devices.

SDP and Zero Trust Architecture (ZTA)

SDP implements Zero Trust Architecture (ZTA), also known as Zero Trust Security Model. Conceptually, ZTA relies on two main ideas.

• No trust without verification. Network security systems trust no devices or people by default. Only previously authenticated and verified clients can access the network. 
• The principle of least privilege. The user only has access to the necessary resources rather than the entire infrastructure.

The latter principle promotes micro-segmentation of data, resources, and software applications. Granting access to what the user needs for specific tasks leaves other segments secure from potential unauthorized access.

Zero Trust Network Access (ZTNA) and SDP are specific applications of the ZTA strategy. Governmental agencies and the cybersecurity community continuously promote the need for such robust security measures.

The non-governmental association Cloud Security Alliance (CSA) leads the way in advancing the conceptual framework for these measures.

How does SDP work?

SDP utilizes various software applications to segment the system and provide secure access to authenticated users. The user can then access that compartment which is necessary for their tasks.

The process of granting access to the user goes like this:

1. Identity verification. SDP typically authenticates users using an integrated third-party identity provider (IdP). Some SDP systems use multi-factor authentication with a hardware token for increased security.
2. Device verification. SDP performs various security checks on the device that is trying to connect. These involve scanning for malware and verifying that the software runs the latest version.
3. Controller approval. The SDP controller is the component that does all the checking. It acts as the gatekeeper between the user's device and the system. Finding everything in order, the controller sends its approval to the SDP gateway.
4. Establishing a secure connection. Having received the SDP controller's approval, the SDP gateway lets the user in. This means establishing a secure connection between the user's device and the services within the system that the user needs. Transport Layer Security (TLS) protocol encrypts the traffic. Here, SDP might also utilize VPN services. The connection is not shared with any other devices or servers.
5. Closed network. The user only has access to a limited set of applications and functions they need for the task. These resources and the user's device form a closed encrypted network that no one else can discover.

SDP vs. VPN: comparing what?

After learning the basic principles of SDP, we are almost ready for the SDP vs. VPN comparison. But first, we need to clarify what functions this comparison applies. 

For this purpose, it is worthwhile to have a quick reminder of what a VPN is.

VPN definition

A Virtual Private Network (VPN) is a mechanism for establishing a secure network connection. It can connect two networks or provide network access to a computing device. The connection uses a public network, such as the Internet, but creates privacy by encrypting traffic.

Thus defined, remote access VPN operates in the same area of granting remote access as SDP. However, this is only part of what a VPN does.

SDP's primary function is to secure an organization's network by granting limited remote access to users. As such, it is comparable to remote access VPNs that fulfill the same function. 

Thus, the SDP vs. VPN comparison only applies to granting organizational users remote access to the organization's resources.

VPN vs. SDP: what are SDP's benefits?

Having clarified where the SDP vs. VPN comparison makes sense, we can name the benefits of SDP in organizational cybersecurity.

• More robust security. SDP's zero trust policy is stricter than the encryption-based security that VPN advances.
• Scalability. SDPs are easy to manage and scale up or down according to the changing needs. Remote VPNs can be harder to scale without losing speed or investing a lot into hardware infrastructure.
• Network micro-segmentation. SDP allows seamless segmenting of the access it gives to personnel. Users can only reach the resources they need while the rest of the network stays hidden. Common VPN solutions provide full remote access to the private networks they create.
• Comprehensive risk assessment. When verifying, SDP scans for malware and considers the device's physical location and software version to identify risks. VPNs do not check for the device’s health.
• Isolating applications. In case of infection, SDP can reduce the threat surface by separating applications from the rest of the network. Additionally, it can obscure critical resources from the rest of the network without hindering authorized access. VPN’s functions usually do not include such isolation of applications.

SDP vs. VPN: can they work together?

VPN technology has been the staple for secure remote access to the organization's internal networks for years. Therefore, many organizations have already invested in creating a VPN-based cybersecurity system.

Completely and quickly switching to unfamiliar SDP technology can require additional resources and time. Thus, rather than thinking in terms of "SDP vs. VPN," organizations might want to integrate the two technologies. Is this possible?

Simply put, the answer is yes. Some SDP tools already use VPN for encryption purposes.

If your organization currently uses an advanced VPN solution, throwing it away is unnecessary. Working with your cybersecurity team, you can probably integrate your VPN into a Zero Trust Architecture built with SDP.