A partially known environment is a type of penetration test where the tester has some information about the target, such as the IP address, the operating system, or the devicetype. This can help the tester focus on specific vulnerabilities and reduce the scope of the test. A partially known environment is also called a gray box test1.
References: CompTIA Security+ Certification Kit: Exam SY0-701, 7th Edition, Chapter 10, page 543.

A high-availability network is a network that is designed to minimize downtime and ensure continuous operation of critical services and applications. To achieve this goal, a high-availability network must consider two important factors: ease of recovery and attack surface.
Ease of recovery refers to the ability of a network to quickly restore normal functionality after a failure, disruption, or disaster. A high-availability network should have mechanisms such as redundancy, failover, backup, and restore to ensure that any single point of failure does not cause a complete network outage. A high-availability network should also have procedures and policies for incident response, disaster recovery, and business continuity to minimize the impact of any network issue on the organization's operations and reputation.
Attack surface refers to the exposure of a network to potential threats and vulnerabilities. A high-availability network should have measures such as encryption, authentication, authorization, firewall, intrusion detection and prevention, and patch management to protect the network from unauthorized access, data breaches, malware, denial-of-service attacks, and other cyberattacks. A high-availability network should also have processes and tools for risk assessment, threat intelligence, vulnerability scanning, and penetration testing to identify and mitigate any weaknesses or gaps in the network security.
References: CompTIA Security+ Study Guide: Exam SY0-701, 9th Edition, Chapter 4: Architecture and Design, pages 164-1651. CompTIA Security+ Certification Kit: Exam SY0-701, 7th Edition, Chapter 4:
Architecture and Design, pages 164-1652.

Data classification is a process of categorizing data based on its level of sensitivity, value, and impact to the organization if compromised. Data classification helps to determine the appropriate security controls and policies to protect the data from unauthorized access, disclosure, or modification. Different organizations may use different data classification schemes, but a common one is the four-tier model, which consists of the following categories: public, private, sensitive, and critical.
Public data is data that is intended for public access and disclosure, and has no impact to the organization if compromised. Examples of public data include marketing materials, press releases, and public web pages.
Private data is data that is intended for internal use only, and has a low to moderate impact to the organization if compromised. Examples of private data include employee records, financial reports, and internal policies.
Sensitive data is data that is intended for authorized use only, and has a high impact to the organization if compromised. Examples of sensitive data include personal information, health records, and intellectual property.
Critical data is data that is essential for the organization's operations and survival, and has a severe impact to the organization if compromised. Examples of critical data include encryption keys, disaster recovery plans, and system backups.
Patient data is a type of sensitive data, as it contains personal and health information that is protected by law and ethical standards. Patient data should be used only by authorized personnel for legitimate purposes, and should be secured from unauthorized access, disclosure, or modification. Therefore, the systems administrator should use the sensitive data classification to secure patient data.
References = CompTIA Security+ SY0-701 Certification Study Guide, page 90-91; Professor Messer's CompTIA SY0-701 Security+ Training Course, video 5.5 - Data Classifications, 0:00 - 4:30.

A hash is an algorithm used to verify data integrity by generating a fixed-size string of characters from input data. If even a single bit of the input data changes, the hash value will change, allowing users to detect any modification to the data. Hashing algorithms like SHA-256 and MD5 are commonly used to ensure data has not been altered.
References:
* CompTIA Security+ SY0-701 Course Content: Domain 6: Cryptography and PKI, which discusses the role of hashing in verifying data integrity.

The tool that the network administrator deployed is described as one that logs suspicious websites and sends a daily report based on various weighted metrics. This fits the description of a detective control. Detective controls are designed to identify and log security events or incidents after they have occurred. By analyzing these logs and generating reports, the tool helps in detecting potential security breaches, thus allowing for further investigation and response.
References = Based on the CompTIA Security+ SY0-701 Resources, specifically under the domain of Security Operations, which discusses different types of security controls, including detective controls.