Zero Trust Security - Never Trust, Always Verify

About 2 min read

Zero trust is a security model that trusts no access and verifies everything, regardless of whether it originates inside or outside the network. Whereas traditional perimeter-based security assumed that "the internal network is safe," zero trust takes "Never Trust, Always Verify" as its core principle. As remote work spread and cloud services expanded, the 2020s saw the very assumption that "inside the perimeter is safe" removed from corporate security design. That said, because it means rebuilding authentication, device management, and networking across an entire company, many organizations have declared zero trust as a direction while still migrating in stages.

Historical Background

The concept of zero trust was proposed in 2010 by John Kindervag, an analyst at Forrester Research. At the time, perimeter-based security (the castle-and-moat model) was mainstream, but a series of perimeter breaches by insider attacks and APTs (Advanced Persistent Threats) exposed the limits of the assumption that "the inside is safe." When remote work expanded rapidly during the 2020 COVID-19 pandemic, the boundary of the corporate network itself became blurred, accelerating the adoption of zero trust. In 2021, the U.S. government issued an executive order requiring federal agencies to adopt zero trust.

Basic Principles

The essence of zero trust lies in three principles. First, access to every resource requires authentication and authorization, regardless of location or network. Second, based on the principle of least privilege, users and devices are granted only the minimum access rights necessary. Third, all traffic is inspected and logged to detect anomalous behavior. Through these principles, threats from inside and lateral movement can be effectively prevented.

Real-World Use Cases

For a company, moving to zero trust rarely fits into a single year; it is normally broken into stages across multiple years. A common order is to first replace the VPN used to enter the internal network with ZTNA (Zero Trust Network Access), shifting authorization to a per-access decision, and only then move on to microsegmentation, which partitions the interior of the network. Doing it in the reverse order leaves the "get inside the perimeter and you can roam" state intact while adding internal partitions, so the payoff tends to be small relative to the operational effort. The same thinking applies to personal use: the closest habit is judging by authentication and device state each time, rather than by "I am on this network, so it is safe."

Architecture Concept Diagram

Practice and Pitfalls in the Field

A common misconception when adopting zero trust is the idea that "you can achieve it just by buying a product." Zero trust is not a specific product but a security design philosophy, realized by combining multiple technologies such as multi-factor authentication, microsegmentation, and continuous monitoring. The zero trust mindset can also be applied at the individual level. Setting a unique, strong password for every service and enabling two-factor authentication is the personal version of the "always verify" principle. By generating a different random password for each service and using a VPN to encrypt your communications, you can build a zero-trust-style security posture even at the individual level.