Zero Trust Network Design

**Issue 1 – We Connect First and Then Authenticate**

• Connect first, authenticate second.

TCP/IP is a fundamentally open network protocol facilitating easy connectivity and reliable communications between distributed computing nodes. It has served us well in enabling our hyper-connected world but—for various reasons—doesn’t include security as part of its core capabilities.

• TCP has a weak security foundation

Transmission Control Protocol (TCP) has been around for decades and has a weak security foundation. When it was created, security was out of scope. TCP can detect and retransmit error packets but leave them to their default; communication packets are not encrypted, which poses security risks.

In addition, TCP operates with a Connect First, Authenticate, Second operation model, which is inherently insecure. It leaves the two connecting parties wide open for an attack. When clients want to communicate and access an application, they first set up a connection.

The authentication stage occurs only once the connect stage has been completed. Once the authentication stage has been completed, we can pass the data. 

From a security perspective, the most important thing to understand is that this connection occurs purely at a network layer with no identity, authentication, or authorization. The beauty of this model is that it enables anyone with a browser to easily connect to any public web server without requiring any upfront registration or permission. This is a perfect approach for a public web server but a lousy approach for a private application.

Zero Trust Connectivity: Service Networking APIs

**Understanding Zero Trust: A Paradigm Shift in Security**

In the context of service networking APIs, zero trust ensures that only authorized users and devices can interact with the APIs, reducing the risk of unauthorized access and data breaches. Implementing zero trust can significantly enhance the security posture of an organization, safeguarding sensitive data and maintaining user trust.

**Integrating Google Cloud and Zero Trust for Enhanced API Security**

Combining Google Cloud’s robust platform with zero trust principles creates a powerful synergy for securing service networking APIs. Google Cloud’s identity and access management tools, such as Cloud Identity and Access Management (IAM), work seamlessly within a zero trust framework to enforce strict authentication and authorization policies. By leveraging these tools, organizations can create a secure environment where APIs are protected from potential threats, and data is kept confidential and integral.

**The potential for malicious activity**

With this process of Connect First and Authenticate Second, we are essentially opening up the door of the network and the application without knowing who is on the other side. Unfortunately, with this model, we have no idea who the client is until they have carried out the connect phase, and once they have connected, they are already in the network. Maybe the requesting client is not trustworthy and has bad intentions. If so, once they connect, they can carry out malicious activity and potentially perform data exfiltration. 

What is Network Monitoring?

Network monitoring is observing and analyzing network components and traffic to identify anomalies or performance issues. It uses specialized software and tools that provide real-time insights into network health, bandwidth utilization, device status, etc. By actively monitoring the network infrastructure, businesses can proactively detect and resolve issues before they escalate.

Network monitoring plays a pivotal role in safeguarding sensitive data from external threats. By monitoring network traffic for any suspicious activities or unauthorized access attempts, IT teams can quickly detect and respond to potential security breaches. Additionally, monitoring network devices for vulnerabilities and applying necessary patches and updates ensures a robust defense against cyber threats.

**Understanding Network Scanning**

Network scanning, at its core, involves systematically examining a network to identify its assets, configurations, and potential vulnerabilities. By employing various scanning techniques, security professionals can understand the network’s structure and potential risks.

Different methodologies for conducting network scanning exist, each catering to specific objectives. Passive scanning, for instance, focuses on observing network traffic without actively engaging with devices. On the other hand, active scanning involves sending requests to network devices to gather information about their configurations and potential vulnerabilities.

Numerous powerful tools are available to aid in network scanning endeavors. From widely used tools like Nmap and Wireshark to more specialized ones like Nessus and OpenVAS, the selection of tools depends on the desired scanning approach and the level of detail required. These tools provide many features, including port scanning, vulnerability assessment, and network mapping capabilities.

Additional Information on Network Mapping

Example: Identifying and Mapping Networks

To troubleshoot the network effectively, you can use a range of tools. Some are built into the operating system, while others must be downloaded and run. Depending on your experience, you may choose a top-down or a bottom-up approach.

**Developing a Zero Trust Architecture**

A zero-trust architecture requires endpoints to authenticate and be authorized before obtaining network access to protected servers. Then, real-time encrypted connections are created between requesting systems and application infrastructure. With a zero-trust architecture, we must establish trust between the client and the application before the client can set up the connection. Zero Trust is all about trust – never trust, always verify.

Trust is bidirectional between the client and the Zero Trust architecture (which can take forms ) and the application to the Zero Trust architecture. It’s not a one-time check; it’s a continuous mode of operation. Once sufficient trust has been established, we move into the next stage, authentication. Once authentication has been set, we can connect the user to the application. Zero Trust access events flip the entire security model and make it more robust. 

• We have gone from connecting first and authenticating second to authenticating first and connecting second.

Example of a zero-trust network access

A. Single Pack Authorization ( SPA)

The user cannot see or know where the applications are located. SDP hides the application and creates a “dark” network by using Single Packet Authorization (SPA) for the authorization.

SPAs, also known as Single Packet Authentication, aim to overcome the open and insecure nature of TCP/IP, which follows a “connect then authenticate” model. SPA is a lightweight security protocol that validates a device or user’s identity before permitting network access to the SDP. The purpose of SPA is to allow a service to be darkened via a default-deny firewall.

The systems use a One-Time-Password (OTP) generated by algorithm 14 and embed the current password in the initial network packet sent from the client to the Server. The SDP specification mentions using the SPA packet after establishing a TCP connection. In contrast, the open-source implementation from the creators of SPA15 uses a UDP packet before the TCP connection.

B. Understanding Port Knocking

At its core, port knocking is an access control method that conceals open ports on a server. Instead of leaving ports visibly open and vulnerable to attackers, port knocking requires a sequence of connection attempts to predefined closed ports. Once the correct sequence is detected, the server dynamically opens the desired port and allows access. This covert approach adds an extra layer of protection, making it an intriguing choice for those seeking to fortify their network security.

Implementing port knocking within a zero-trust framework can significantly enhance your network security. By obscuring open ports and allowing access only to authorized users who possess the correct port-knocking sequence, potential attackers face an additional barrier to overcome. This technique effectively reduces the attack surface and minimizes the risk of unauthorized access, making it an invaluable tool for security-conscious individuals and organizations.

**Issue 2 – Fixed perimeter approach to networking and security**

Traditionally, security boundaries were placed at the edge of the enterprise network in a classic “castle wall and moat” approach. However, as technology evolved, remote workers and workloads became more common. As a result, security boundaries necessarily followed and expanded from just the corporate perimeter.

**The traditional world of static domains**

The traditional world of networking started with static domains. Networks were initially designed to create internal segments separated from the external world by a fixed perimeter. The classical network model divided clients and users into trusted and untrusted groups. The internal network was deemed trustworthy, whereas the external was considered hostile.

The perimeter approach to network and security has several zones. We have, for example, the Internet, DMZ, Trusted, and then Privileged. In addition, we have public and private address spaces that separate network access from here. Private addresses were deemed more secure than public ones as they were unreachable online. However, this trust assumption that all private addresses are safe is where our problems started. 

**The fixed perimeter** 

The digital threat landscape is concerning. We are getting hit by external threats to your applications and networks from all over the world. They also come internally within your network, and we have insider threats within a user group and internally as insider threats across user group boundaries. These types of threats need to be addressed one by one.

One issue with the fixed perimeter approach is that it assumes trusted internal and hostile external networks. However, we must assume that the internal network is as hostile as the external one.

Over 80% of threats are from internal malware or malicious employees. The fixed perimeter approach to networking and security is still the foundation for most network and security professionals, even though a lot has changed since the design’s inception. 

Zero Trust & VPC Service Controls

### Role of VPC Service Controls in Zero Trust Network Design

Zero Trust Network Design is rapidly gaining traction as an essential cybersecurity framework. Unlike traditional security models that assume trust within the network, Zero Trust operates on the principle of ‘never trust, always verify.’ This paradigm shift emphasizes the need for more granular controls and continuous verification of user and device identities. VPC Service Controls align perfectly with this approach by restricting access to critical resources and ensuring that only authenticated and authorized entities can interact with the data. This integration fortifies the network’s defenses, minimizes potential attack vectors, and ensures data integrity.

### Implementing VPC Service Controls in Google Cloud

Implementing VPC Service Controls within Google Cloud is a strategic move for organizations aiming to enhance their security posture. The process involves setting up security perimeters around sensitive resources, such as Cloud Storage buckets, BigQuery datasets, and Cloud Bigtable instances. By defining these perimeters, organizations can enforce policies that restrict access based on specific criteria, such as IP addresses, service accounts, or even user-defined attributes. This granular control not only prevents unauthorized access but also ensures compliance with industry regulations and standards.

We get hacked daily!

We are now at a stage where 45% of US companies have experienced a data breach. The 2022 Thales Data Threat Report found that almost half (45%) of US companies suffered a data breach in the past year. However, this could be higher due to the potential for undetected breaches.

We are getting hacked daily, and major networks with skilled staff are crashing. Unfortunately, the perimeter approach to networking has failed to provide adequate security in today’s digital world. It works to an extent by delaying an attack. However, a bad actor will eventually penetrate your guarded walls with enough patience and skill.

If a large gate and walls guard your house, you would feel safe and fully protected inside. However, the perimeter protecting your home may be as large and thick as possible. There is still a chance that someone can climb the walls, access your front door, and enter your property. If a bad actor cannot even see your house, they cannot take the next step and try to breach your security.

Example: Security Scan Lynis

Lynis is an open-source security auditing tool designed to assess the security of Linux and Unix-based systems. Developed by CISOfy, Lynis performs comprehensive security scans by analyzing system configurations, checking for vulnerabilities, and recommending steps to improve overall security posture.

**Issue 3 – Dissolved perimeter caused by the changing environment**

The environment has changed with the introduction of the cloud, advanced BYOD, machine-to-machine connections, the rise in remote access, and phishing attacks. We have many internal devices and a variety of users, such as on-site contractors, that need to access network resources.

Corporate devices are also trending to move to the cloud, collocated facilities, and off-site to customer and partner locations. In addition, they are becoming more diversified with hybrid architectures.

These changes are causing major security problems with the fixed perimeter approach to networking and security. For example, with the cloud, the internal perimeter is stretched to the cloud, but traditional security mechanisms are still being used. But it is an entirely new paradigm. Also, some abundant remote workers work from various devices and places.

Again, traditional security mechanisms are still being used. As our environment evolves, security tools and architectures must evolve. Let’s face it: the network perimeter has dissolved as your remote users, things, services, applications, and data are everywhere. In addition, as the world moves to the cloud, mobile, and IoT, the ability to control and secure everything in the network is no longer available.

Phishing attacks are on the rise.

We have witnessed increased phishing attacks that can result in a bad actor landing on your local area network (LAN). Phishing is a type of social engineering where an attacker sends a fraudulent message designed to trick a person into revealing sensitive information to the attacker or to deploy malicious software on the victim’s infrastructure, like ransomware. The term “phishing” was first used in 1994 when a group of teens worked to obtain credit card numbers from unsuspecting users on AOL manually.

Hackers are inventing new ways.

By 1995, they had created a program called AOHell to automate their work. Since then, hackers have continued to invent new ways to gather details from anyone connected to the internet. These actors have created several programs and types of malicious software that are still used today.

Recently, I was a victim of a phishing email. Clicking and downloading the file is very easy if you are not educated about phishing attacks. In my case, the particular file was a .wav file. It looked safe, but it was not.

**Issue 4 – Broad-level access**

So, you may have heard of broad-level access and lateral movements. Remember, with traditional network and security mechanisms, when a bad actor lands on a particular segment, i.e., a VLAN, known as zone-based networking, they can see everything on that segment. So, this gives them broad-level access. But, generally speaking, when you are on a VLAN, you can see everything in that VLAN and VLAN-to-VLAN communication is not the hardest thing to do, resulting in lateral movements.

The issue of lateral movements

Lateral movement is the technique attackers use to progress through the organizational network after gaining initial access. Adversaries use lateral movement to identify target assets and sensitive data for their attack. Lateral movement is the tenth step in the MITRE Att&ck framework. It is the set of techniques attackers use to move in the network while gaining access to credentials without being detected.

No intra-VLAN filtering

This is made possible as, traditionally, a security device does not filter this low down on the network, i.e., inside of the VLAN, known as intra-VLAN filtering. A phishing email can easily lead the bad actor to the LAN with broad-level access and the capability to move laterally throughout the network. 

For example, a bad actor can initially access an unpatched central file-sharing server; they move laterally between segments to the web developers’ machines and use a keylogger to get the credentials to access critical information on the all-important database servers.

They can then carry out data exfiltration with DNS or even a social media account like Twitter. However, firewalls generally do not check DNS as a file transfer mechanism, so data exfiltration using DNS will often go unnoticed. 

With a zero-trust network segmentation approach, networks are segmented into smaller islands with specific workloads. In addition, each segment has its own ingress and egress controls to minimize the “blast radius” of unauthorized access to data.

Example: Segmentation with Network Endpoint Groups (NEGs)

**Issue 5 – The challenges with traditional firewalls**

The limited world of 5-tuple

Traditional firewalls typically control access to network resources based on source IP addresses. This creates the fundamental challenge of securing admission. Namely, we need to solve the user access problem, but we only have the tools to control access based on IP addresses.

As a result, you have to group users, some of whom may work in different departments and roles, to access the same service and with the same IP addresses. The firewall rules are also static and don’t change dynamically based on levels of trust on a given device. They provide only network information.

Maybe the user moves to a more risky location, such as an Internet cafe, its local Firewall, or antivirus software that has been turned off by malware or even by accident. Unfortunately, a traditional firewall cannot detect this and live in the little world of the 5-tuple.  Traditional firewalls can only express static rule sets and not communicate or enforce rules based on identity information.

**Issue 6 – A Cloud-focused environment**

Upon examining the cloud, let’s compare a public parking space. A public cloud is where you can put your car compared to your vehicle in your parking garage. We have multiple tenants who can take your area in a public parking space, but we don’t know what they can do to your car.

Today, we are very cloud-focused, but when moving applications to the cloud, we need to be very security-focused. However, the cloud environment is less mature in providing the traditional security control we use in our legacy environment. 

So, when putting applications in the cloud, you shouldn’t leave security to its default. Why? Firstly, we operate in a shared model where the tenant after you can steal your encryption keys or data. There have been many cloud breaches. We have firewalls with static rulesets, authentication, and key management issues in cloud protection.

**Control point change**

One of the biggest problems is that the perimeter has moved when you move to a cloud-based application. Servers are no longer under your control. Mobile and tablets exacerbate the problem as they can be located everywhere. So, trying to control the perimeter is very difficult. More importantly, firewalls only have access to and control network information and should have more content.

This perimeter is defined by ZTNA architecture and software-defined perimeter. Cloud users now manage firewalls by moving their applications to the cloud, not the I.T. teams within the cloud providers.

So when moving applications to the cloud, even though cloud providers provide security tools, the cloud consumer has to integrate security to have more visibility than they have today.

Before, we had clear network demarcation points set by a central physical firewall creating inside and outside trust zones. Anything outside was considered hostile, and anything on the inside was deemed trusted.

1. Connection-centric model

The Zero Trust model flips this around and considers everything untrusted. To do this, there are no longer pre-defined fixed network demarcation points. Instead, the network perimeter initially set in stone is now fluid and software-based.

Zero Trust is connection-centric, not network-centric. Each user on a specific device connected to the network gets an individualized connection to a particular service hidden by the perimeter.

Instead of having one perimeter every user uses, SDP creates many small perimeters purposely built for users and applications. These are known as micro perimeters. Clients are cryptographically signed into these microperimeters.

2. Micro perimeters: Zero trust network segmentation

The micro perimeter is based on user and device context and can dynamically adjust to environmental changes. So, as a user moves to different locations or devices, the Zero Trust architecture can detect this and set the appropriate security controls based on the new context.

The data center is no longer the center of the universe. Instead, the user on specific devices, along with their service requests, is the new center of the universe.

Zero Trust does this by decoupling the user and device from the network. The data plane is separated from the network to remove the user from the control plane, where the authentication happens first.

Then, the data plane, the client-to-application connection, transfers the data. Therefore, the users don’t need to be on the network to gain application access. As a result, they have the least privilege and no broad-level access.

3. Zero trust network segmentation

Zero-trust network segmentation is gaining traction in cybersecurity because it increases an organization’s network protection. This method of securing networks is based on the concept of “never trust, always verify,” meaning that all traffic must be authenticated and authorized before it can access the network.

This is accomplished by segmenting the network into multiple isolated zones accessible only through specific access points, which are carefully monitored and controlled.

Network segmentation is a critical component of a zero-trust network design. By dividing the network into smaller, isolated units, it is easier to monitor and control access to the network. Additionally, segmentation makes it harder for attackers to move laterally across the network, reducing the chance of a successful attack.

Zero-trust network design segmentation is essential to any organization’s cybersecurity strategy. By utilizing segmentation, authentication, and monitoring systems, organizations can ensure their networks are secure and their data is protected.

4. The I.P. address conundrum

Everything today relies on IP addresses for trust, but there is a problem: IP addresses lack user knowledge to assign and validate the device’s trust. There is no way for an IP address to do this. IP addresses provide connectivity but do not involve validating the trust of the endpoint or the user.

Also, I.P. addresses should not be used as an anchor for network locations as they are today because when a user moves from one place to another, the I.P. address changes. 

Can’t have security related to an I.P. address.

But what about the security policy assigned to the old IP addresses? What happens with your changed IPs? Anything tied to IP is ridiculous, as we don’t have a good hook to hang things on for security policy enforcement. There are several facets to policy. For example, the user access policy touches on authorization, the network access policy touches on what to connect to, and the user account policies touch on authentication.

With either one, there is no policy visibility with I.P. addresses. This is also a significant problem for traditional firewalling, which displays static configurations; for example, a stationary design may state that this particular source can reach this destination using this port number. 

**Security-related issues to I.P.**

1. This has no meaning. There is no indication of why that rule exists or under what conditions a packet should be allowed to travel from one source to another.
2. No contextual information is taken into consideration. When creating a robust security posture, we must consider more than ports and IP addresses.

For a robust security posture, you need complete visibility into the network to see who, what, when, and how they connect with the device. Unfortunately, today’s Firewall is static and only contains information about the network.

On the other hand, Zero Trust enables a dynamic firewall with the user and device context to open a firewall for a single secure connection. The Firewall remains closed at all other times, creating a ‘black cloud’ stance regardless of whether the connections are made to the cloud or on-premise. 

The rise of the next-generation firewall?

Next-generation firewalls are more advanced than traditional firewalls. They use the information in layers 5 through 7 (session, presentation, and application layers) to perform additional functions. They can provide advanced features such as intrusion detection, prevention, and virtual private networks.

Today, most enterprise firewalls are “next generation” and typically include IDS/IPS, traffic analysis and malware detection for threat detection, URL filtering, and some degree of application awareness/control.

Like the NAC market segment, vendors in this area began a journey to identity-centric security around the same time Zero Trust ideas began percolating through the industry. Today, many NGFW vendors offer Zero Trust capabilities, but many operate with the perimeter security model.

Still, IP-based security systems

NGFWs are still IP-based systems offering limited identity and application-centric capabilities. In addition, they are static firewalls. Most do not employ zero-trust segmentation, and they often mandate traditional perimeter-centric network architectures with site-to-site connections and don’t offer flexible network segmentation capabilities. Similar to conventional firewalls, their access policy models are typically coarse-grained, providing users with broader network access than what is strictly necessary.

Example: Tags and Controls with firewalling