As business started to connect to the Internet, this connection point became the natural place to enforce security controls, mimicking existing physical security models. Businesses assumed that if someone was inside the building or inside a certain perimeter, that person inherently had a higher level of trust than those outside.
The same business needs that required connectivity forced erosion of this perimeter. Websites and email servers had to be reached from outside of the defenses. Additional perimeters were created to address this, starting with DMZ networks. Some users and data moved to the untrusted side of the walls, and attacks were originating from the inside (whether from phishing, compromised credentials, or insiders). More perimeters were created, including data center firewalls and internal segmentation or even microsegmentation deployments.
With the pandemic, the erosion of the perimeter turned into a collapse. Instead of some data and a few users being outside the perimeter, there was an almost overnight need to have all the employees outside. The new demands weren't easy: access to all the data, from all the places, all the time, on all the devices. Securely.
The New Perimeters
Identity as a Perimeter
Identity has been a key part of security forever. The importance of strong identity has increased exponentially with digital transformations — for a software-as-as-security (SaaS) application, it may be the only control in the hands of the data owners.
The scope of "identity" has grown from who you are to include physical location, the device being connected from and its state, the time of day, and other parameters. Multifactor authentication has become a minimum standard, while role-based access based on "extended" identity enforces policy once the connection is established.
There are limitations to the "identity-as-a-perimeter" concept; not everything is in SaaS applications, and additional controls (such as data leakage prevention) may be needed and must be in the application itself.
Endpoint as a Perimeter
Before firewalls, security was controlled at the endpoint — and what is old is new again. Modern endpoint solutions provide software asset inventory, threat prevention, and advanced attack detection backed by machine learning and artificial intelligence. The endpoint perimeter is much more robust than in the past.
Agents on the endpoint can provide more benefits as well, just like the traditional perimeter. Functions such as asset management, software management, vulnerability management, and data leakage prevention are all possible extensions of the "endpoint perimeter," though you may need many agents to support many functions.
Secure Access Service Edge
Secure access service edge (SASE) is a framework that moves security controls closer to where the user meets the data. Data is increasingly stored in cloud applications, so the SASE frameworks add security controls on the cloud edge. The framework can support a range of services to protect data and applications both in the cloud and on-premises.
Integral to this concept is the identity of the user and that person's rights as well as the assurance that the endpoint is "appropriately" secure for the access the user is getting. SASE frameworks must incorporate identity and endpoint elements to work most effectively.
Zero-Trust Network Architecture
The culmination of the "perimeterless network" is a zero-trust networking architecture (ZTNA). In a zero-trust environment, every connection is presumed hostile until proven friendly — a "never trust, always verify" model in which connections will only be allowed on a least-privilege basis, closely inspected, and all activities and traffic will be logged.
As a design philosophy, ZTNA informs all the above choices and make them more effective — though doing so while maintaining a relatively frictionless end-user experience is no easy task and doesn't get easier with scale.
…and the Legacy Perimeter
The legacy Internet edge perimeter and the existing internal perimeters are not yet completely obsolete. Some resources and users reside and will continue to reside on-premises and need protection. It's just that they aren't the single control that they were before. Defense in depth is hugely important and will likely include "legacy" controls for the foreseeable future as part of a comprehensive multiperimeter strategy.
So, What's My "New Perimeter"?
This is the perfect place for the engineer's favorite answer: "It depends." The new perimeter is going to depend on the state of digital transformation, the locations of your data, your risk tolerance, and the type of endpoints you're using. Your solution is going to have to be built and designed to meet your unique needs, objectives, and risks. It must be as frictionless as possible to your users and simultaneously minimize the attack surface. It's not easy, but it's possible.