Zero Trust is an information security model that assumes there are no trusted entities within or outside an organization's network perimeter, whether they are employees, contractors, or other stakeholders.

Instead of relying solely on a traditional castle-and-moat approach (where the internal network is protected by firewalls and intrusion detection systems), Zero Trust emphasizes continuous verification of every user, device, and system before granting access to resources.

The main principles of Zero Trust include:

Least Privilege Access 

Users should only have the minimum level of access necessary for their job functions.

This reduces the potential damage from a compromised account or stolen credentials.

Micro-Segmentation 

Divide your network into smaller segments, each with its own security controls and policies.

This limits the spread of threats in case one segment is breached.

Continuous Monitoring and Adaptive Response 

Regularly monitor all activity within your environment for any signs of suspicious behavior or anomalies.

Implement automated response systems to detect, contain, and remediate potential threats in real-time.

Multi-Factor Authentication (MFA) 

Require users to provide at least two forms of identification before granting access - something they know (like a password), something they have (like a physical token or smartphone app), and something they are (biometric data).

Encryption Everywhere 

Encrypt all data, both in transit and at rest, to protect sensitive information from unauthorized access.

To audit a small business' tech stack, follow these steps:

Identify the Current Infrastructure 

Make an inventory of all hardware (servers, desktops, laptops), software applications, and cloud services used by the organization.

This includes operating systems, productivity tools, customer relationship management (CRM) systems, accounting software, etc.

Assess Security Controls 

Evaluate each component of your tech stack for its security features.

Look at firewalls, antivirus programs, intrusion detection/prevention systems, data encryption methods, and access controls.

Identify any gaps in the current setup that could leave the organization vulnerable to attacks or breaches.

Review Security Policies

Examine existing security policies for their comprehensiveness and alignment with industry best practices.

Look at password policies, incident response plans, data backup procedures, etc. Identify any areas where policy improvements could be made.

Conduct Vulnerability Scans 

Use automated tools to scan your network and systems for known vulnerabilities.

This can help you identify potential weaknesses that attackers might exploit.

Perform Penetration Testing 

Simulate a real-world cyberattack by attempting to breach your system using the same techniques an actual hacker would use.

This can reveal any unidentified vulnerabilities and help you understand how effective your current security measures are.

Interview Employees 

Speak with employees about their understanding of company security policies, their experiences with cybersecurity incidents (if any), and their awareness of potential threats like phishing attacks or social engineering tactics.

As for the best tools available on the market to carry out this task, some popular options include:

1. Nessus - A comprehensive vulnerability scanner that can identify weaknesses in your systems and applications.
2. Qualys - Another powerful vulnerability management solution that provides continuous monitoring of your IT environment for security threats.
3. Burp Suite - An integrated platform for web application security testing, including functional analysis, penetration testing, and more.
4. Metasploit - A penetration testing framework used to identify vulnerabilities in networks, applications, and operating systems by simulating cyberattacks.
5. SolarWinds Network Performance Monitor - An IT infrastructure monitoring tool that helps you detect network issues, optimize performance, and secure your environment against threats.
6. LastPass - A password manager to help manage and protect passwords across different systems and applications.
7. Duo Security - Provides multi-factor authentication solutions for organizations of all sizes.