Network security can be referred to as the act of protecting an organisation's network infrastructure from attacks or damage. The concept of network security plays a vital role in the confidentiality, integrity, and authentication of a network system.
The network security concept covers Intrusion detection systems, traffic analysis, AAA, network monitoring, CIA, etc. [1]

DDOS (Distributed-Denial-of-Service) This attack occurs when a threat actor build sets up different botnets (large fleets of compromised systems) to direct false traffic like huge volumes of SYN/ACC packets toward a server or a network, this traffic overwhelms the server by carrying out complex SQL queries, making the database weak and vulnerable.

Ransomware: Ransomware attacks usually occur when an attacker successfully encrypts a victim's data and demands a ransom for the decryption key. Oftentimes, paying the ransom doesn't necessarily guarantee full recovery of the data and may encourage further attacks and extortion by the attacker.

Cryptojacking: This attack occurs when attackers use malware to take over a victim's computer or device to mine cryptocurrencies without the victim's knowledge or consent.

Phishing:

Brute Force attack: This attack occurs when attackers make several attempts to gain access to a system or administrator account by systematically trying several possible combinations of credentials ( usernames and passwords) until they find the right combination, thereby gaining access to the system.

Physical Attack: This is an attack on physical hardware or infrastructure, such as cutting data or network cables, or stealing network servers, which can disrupt services and compromise security.

Man-in-the-middle attack: this is an attack that occurs when an attacker intercepts network traffic. An attacker can intercept or eavesdrop on a network between users on a particular network, in order to modify the data being exchanged.

Social Engineering: This often involves the manipulation of individuals into revealing confidential information or performing actions that compromise security. This is done by a skilled hacker who uses techniques like pretexting, baiting, and tailgating to collect confidential data of an organization.

Advanced Persistent Threats (APTs): APTs are long-term, targeted attacks by well-funded and skilled attackers whose aims are to infiltrate networks, often for espionage or data theft. These attackers are often sponsored by private or top-secret government organisations.

Worms and Viruses: These are self-replicating malware that spread from one system to another, often causing damage or stealing data along the way. These threats can spread within seconds and can shut down a system or network.

SQL Injection: an attacker uses SQL injection(sending several SQL queries via the input data from the client base to the application) to exploit vulnerabilities or weaknesses in web applications in order to gain unauthorized access to the database.

C. Tools
Antivirus: This is software that protects the system from malware or ransomware attacks. Examples are Norton, McAfee, Bitdefender, etc.
Procedure: To protect the network, install and regularly update antivirus software on all devices. Schedule regular scans and ensure real-time protection is active.

Firewall: A firewall is a network security tool that monitors and regulates network traffic between computer devices on a network. It can allow or block traffic according to set rules or configuration principles. Examples are Firewalls like Windows Firewall or hardware firewalls.
Procedure: Firewalls must be configured to filter incoming and outgoing network traffic. Access to only necessary ports and services must be restricted.

Intrusion Detection System (IDS) and Intrusion Prevention System (IPS): These are security technologies used to protect computer networks and systems from different types of cyber threats and attacks. Examples of IDS/IPS solutions are Snort, Suricata, etc.

IDS is designed to monitor network traffic and system activities to detect and identify fake or malicious behavior or traffic and potential security breaches. It observes and analyzes network traffic without actively taking action to stop threats, but alerts network admins by generating notifications about potential security breaches or incidents.
IPS functions on the capabilities of the IDS. What this means is that the IPS takes appropriate measures to block, prevent, or mitigate any threats that were detected by the IDS. IPS performs actions blocking IP addressing, and blocking malicious network traffic and ports that attempt to infiltrate the network.

Procedure: Always deploy IDS to detect suspicious activities and IPS to block or prevent malicious traffic and attacks.

Patch Management: This is an important security management tool that identifies, tests, deploys, and monitors updates for software, patches, and fixes for various software applications, operating systems, and hardware devices. Examples are tools like Microsoft WSUS, SCCM, or third-party patch management solutions.
Procedure: Regularly apply security patches and updates to the operating system and software to address known vulnerabilities.

Email Filtering: this is a network security measure that helps to identify and block unwanted or malicious emails from entering a user's inbox. Most emails that end up in the spam folder are emails that were filtered as potential malicious emails.
Email filtering comprises spam filtering, Phishing protection, Malware and Attachment scanning, Sending authentication, etc.

Examples of  Email filtering solutions are Microsoft Exchange Online Protection or third-party spam filters.
Procedure: Implement email filtering to block malicious attachments and detect phishing attempts.

Incident Response Plan: this is a documented plan that outlines the steps to take in the event of an incident, attack or security breach. This plan includes communication, containment, eradication, and recovery.

Security Information and Event Management (SIEM) Systems: these are security platforms that collect and analyze log data from different sources to detect and respond swiftly to security incidents or breaches.

Least Privilege Principle: this is a security measure that grants users, devices, and systems the minimum level of access needed to complete their required tasks successfully. It permits users access to certain levels of rights and privileges in a network system.