Abug bounty programencourages ethical hackers tofind and report vulnerabilities, helping organizations discover security flaws before they are exploited by malicious actors. Unlikevulnerability scans, bug bounty programs usereal-world testing techniques.
Reference:CompTIA Security+ SY0-701 Official Study Guide, Security Operations domain.

A regulatory requirement is a mandate imposed by a government or an authority that must be followed by an organization or an individual. In a banking environment, audits are often required by regulators to ensure compliance with laws, standards, and policies related to security, privacy, and financial reporting. Audits help to identify and correct any gaps or weaknesses in the security posture and the internal controls of the organization.
References:
Official CompTIA Security+ Study Guide (SY0-701), page 507
Security+ (Plus) Certification | CompTIA IT Certifications 2

A legacy server is a server that is running outdated or unsupported software or hardware, which may pose security risks and compatibility issues. A critical business application is an application that is essential for the operation and continuity of the business, such as accounting, payroll, or inventory management. A legacy server running a critical business application may be difficult to replace or upgrade, but it should not be left unsecured or exposed to potential threats.
One of the best ways to handle a legacy server running a critical business application is to harden it.
Hardening is the process of applying security measures and configurations to a system to reduce its attack surface and vulnerability. Hardening a legacy server may involve steps such as:
Applying patches and updates to the operating system and the application, if available Removing or disabling unnecessary services, features, or accounts Configuring firewall rules and network access control lists to restrict inbound and outbound traffic Enabling encryption and authentication for data transmission and storage Implementing logging and monitoring tools to detect and respond to anomalous or malicious activity Performing regular backups and testing of the system and the application Hardening a legacy server can help protect the critical business application from unauthorized access, modification, or disruption, while maintaining its functionality and availability. However, hardening a legacy server is not a permanent solution, and it may not be sufficient to address all the security issues and challenges posed by the outdated or unsupported system. Therefore, it is advisable to plan for the eventual decommissioning or migration of the legacy server to a more secure and modern platform, as soon as possible.
References: CompTIA Security+ SY0-701 Certification Study Guide, Chapter 3: Architecture and Design, Section 3.2: Secure System Design, Page 133 1; CompTIA Security+ Certification Exam Objectives, Domain
3: Architecture and Design, Objective 3.2: Explain the importance of secure system design, Subobjective:
Legacy systems 2

To reduce the number of individual operating systems while decommissioning physical servers, the company should use containerization. Containerization allows multiple applications to run in isolated environments on a single operating system, significantly reducing the overhead compared to running multiple virtual machines, each with its own OS.
* Containerization: Uses containers to run multiple isolated applications on a single OS kernel, reducing the need for multiple OS instances and improving resource utilization.
* Microservices: An architectural style that structures an application as a collection of loosely coupled services, which does not necessarily reduce the number of operating systems.
* Virtualization: Allows multiple virtual machines to run on a single physical server, but each VM requires its own OS, not reducing the number of OS instances.
* Infrastructure as code: Manages and provisions computing infrastructure through machine-readable configuration files, but it does not directly impact the number of operating systems.