Zero Trust Security Model

Zero Trust Security Model

Zero Trust security is an IT security model that requires strict identity verification for every person and device trying to access resources on a private network, regardless of whether they are sitting within or outside of the network perimeter. ZTNA is the main technology associated with Zero Trust architecture; but Zero Trust is a holistic approach to network security that incorporates several different principles and technologies.

More simply : traditional IT network security trusts anyone and anything inside the network. A Zero Trust architecture trusts no one and nothing.

Zero Trust security means that no one is trusted by default from inside or outside the network, and verification is required from everyone trying to gain access to resources on the network. This added layer of security has been shown to prevent data breaches. Studies have shown that the average cost of a single data breach is over $3 million. Considering that figure, it should come as no surprise that many organizations are now eager to adopt a Zero Trust security policy.

What are the main principles behind Zero Trust security?

Continuous monitoring and validation

The philosophy behind a Zero Trust network assumes that there are attackers both within and outside of the network, so no users or machines should be automatically trusted. Zero Trust verifies user identity and privileges as well as device identity and security. Logins and connections time out periodically once established, forcing users and devices to be continuously re-verified.

Least privilege

Another principle of zero trust security is least-privilege access. This means giving users only as much access as they need, like an army general giving soldiers information on a need-to-know basis. This minimizes each user’s exposure to sensitive parts of the network. Implementing least privilege involves careful managing of user permissions. VPNs are not well-suited for least-privilege approaches to authorization, as logging in to a VPN gives a user access to the whole connected network.

Device access control

In addition to controls on user access, Zero Trust also requires strict controls on device access. Zero Trust systems need to monitor how many different devices are trying to access their network, ensure that every device is authorized, and assess all devices to make sure they have not been compromised. This further minimizes the attack surface of the network.


Zero Trust networks also utilize microsegmentation. Microsegmentation is the practice of breaking up security perimeters into small zones to maintain separate access for separate parts of the network. For example, a network with files living in a single data center that utilizes microsegmentation may contain dozens of separate, secure zones. A person or program with access to one of those zones will not be able to access any of the other zones without separate authorization.

Preventing lateral movement

In network security, “lateral movement” is when an attacker moves within a network after gaining access to that network. Lateral movement can be difficult to detect even if the attacker’s entry point is discovered, because the attacker will have gone on to compromise other parts of the network.

Zero Trust is designed to contain attackers so that they cannot move laterally. Because Zero Trust access is segmented and has to be re-established periodically, an attacker cannot move across to other microsegments within the network. Once the attacker’s presence is detected, the compromised device or user account can be quarantined, cut off from further access. (In a castle-and-moat model, if lateral movement is possible for the attacker, quarantining the original compromised device or user has little to no effect, since the attacker will already have reached other parts of the network.)

Multi-factor authentication (MFA)

Multi-factor authentication (MFA) is also a core value of Zero Trust security. MFA means requiring more than one piece of evidence to authenticate a user; just entering a password is not enough to gain access. A commonly seen application of MFA is the 2-factor authorization (2FA) used on online platforms like Facebook and Google. In addition to entering a password, users who enable 2FA for these services must also enter a code sent to another device, such as a mobile phone, thus providing two pieces of evidence that they are who they claim to be.

What is Zero Trust Network Access (ZTNA)?

Zero Trust Network Access (ZTNA) is the technology that makes it possible to implement a Zero Trust security model. “Zero Trust” is an IT security model that assumes threats are present both inside and outside a network. Consequently, Zero Trust requires strict verification for every user and every device before authorizing them to access internal resources.

ZTNA is similar to the software-defined perimeter (SDP) approach to controlling access. In ZTNA, like in SDP, connected devices are not aware of any resources (applications, servers, etc.) on the network other than what they are connected to.

Imagine a scenario in which every resident gets a phone book with the phone numbers of every other resident of their city, and anyone can dial any number to contact any other person. Now imagine a scenario in which everyone has an unlisted phone number and one resident has to know another resident’s phone number in order to call them. This second scenario offers a few advantages: no unwanted calls, no accidental calls to the wrong person, and no risk of unscrupulous persons using the city’s phone book to fool or scam the residents.

ZTNA is like the second scenario. But instead of phone numbers, ZTNA uses “unlisted” IP addresses, applications, and services. It sets up one-to-one connections between users and the resources they need, like when two people who need to contact each other exchange phone numbers. But unlike two people exchanging numbers, ZTNA connections need to be re-verified and recreated periodically.

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