What is network security?

Network security is the collection of policies, technologies, and practices used to protect network infrastructure and the systems that communicate through it. It applies to home Wi-Fi, office networks, data centers, cloud environments, and connections between organizations.

A secure network aims to ensure that only authorized users and devices can access the resources they need, that data is protected during transmission, and that suspicious activity can be detected and investigated.

Network security is not a single product. A firewall cannot replace software updates, and antivirus software cannot replace secure network configuration. Effective protection uses multiple controls that support one another.

Main objectives of network security

Network security supports several important objectives.

Confidentiality

Confidentiality means preventing unauthorized people or systems from accessing sensitive information. Encryption, access restrictions, and secure authentication help protect confidentiality.

Integrity

Integrity means protecting information and configurations against unauthorized modification. Access controls, cryptographic integrity checks, and configuration monitoring can help identify or prevent unwanted changes.

Availability

Availability means ensuring that authorized users can access systems and services when needed. Backups, redundancy, capacity planning, monitoring, and denial-of-service protections can support availability.

These three objectives are commonly known as the CIA triad: confidentiality, integrity, and availability.

Common network security threats

Network threats can target devices, applications, users, data, or the communication paths between systems. Understanding the threat helps determine which defensive controls are appropriate.

Unauthorized access

Attackers may attempt to access network devices or services using stolen credentials, weak passwords, exposed management interfaces, or configuration weaknesses. Strong authentication and restricted management access help reduce this risk.

Malware and ransomware

Malware can enter a network through compromised devices, malicious downloads, vulnerable services, or stolen credentials. Ransomware may encrypt data and disrupt operations. Patching, endpoint protection, network segmentation, least privilege, and tested backups help limit the impact.

Phishing and credential theft

Phishing attempts to trick users into revealing credentials or running malicious content. Stolen accounts can then be used to access internal resources. Multi-factor authentication, user awareness, and sign-in monitoring help reduce the risk.

Denial-of-service attacks

Denial-of-service attacks attempt to make a system or network unavailable by exhausting resources or overwhelming a service with traffic. Capacity planning, filtering, rate limiting, and suitable upstream protection can help defend against such attacks.

Vulnerabilities and misconfiguration

Outdated firmware, unnecessary open ports, weak access rules, default credentials, and incorrect firewall policies can expose a network. Regular updates, configuration reviews, and vulnerability management help identify weaknesses before they are exploited.

Wireless network attacks

Weak Wi-Fi credentials, insecure encryption, unauthorized access points, and poorly separated guest networks can expose wireless environments. Strong authentication, modern encryption, and access point monitoring are important defenses.

Important network security controls

Network defenders use different controls to prevent unwanted access, reduce exposure, and detect suspicious activity.

Firewalls

Firewalls enforce traffic rules based on their capabilities and configuration. They can restrict connections by addresses, ports, connection state, applications, or other properties. Correctly maintained rules help reduce unnecessary network exposure.

Read more in Firewalls and IPS.

Intrusion detection and prevention

Intrusion detection systems analyze activity for possible signs of attacks and generate alerts. Intrusion prevention systems can also block traffic that matches configured prevention rules. These systems need appropriate tuning to reduce false alarms and avoid disrupting legitimate services.

Learn more about intrusion detection.

Access control

Access control determines which users and devices can reach particular resources. Strong passwords, multi-factor authentication, role-based permissions, and least-privilege policies reduce the risk of unauthorized access.

Encryption

Encryption protects data from being read by unauthorized parties when it is stored or transmitted. Secure protocols such as HTTPS and appropriately configured VPNs help protect communications. Encryption does not remove the need to verify identities or secure endpoints.

Network segmentation

Segmentation separates a network into zones with different access requirements. VLANs, routing policies, firewalls, and access controls can restrict unnecessary communication between those zones.

Network segmentation and defense in depth

A flat network allows many devices to communicate within the same broad network environment. If one device is compromised, unnecessary connectivity can make it easier for an attacker to reach additional systems.

Segmentation divides the network into smaller zones and applies rules to communication between them. For example, an organization might separate employee computers, guest Wi-Fi, servers, security cameras, and network management systems.

Segmentation does not automatically make a network secure. Incorrect rules or overly broad permissions can undermine it. Administrators should document permitted communication, review rules regularly, and monitor unexpected connections.

Network monitoring and incident response

Preventive controls cannot guarantee that every attack will be blocked. Network monitoring helps defenders identify unusual behavior, investigate incidents, and determine whether security controls are working as intended.

What should administrators monitor?

• Unusual increases in network traffic or connection attempts.
• Repeated authentication failures and unexpected logins.
• Changes to router, switch, firewall, and access point configurations.
• Unexpected services or devices appearing on the network.
• Traffic to unusual destinations or unexpected network ports.
• Device health, bandwidth utilization, interface errors, and outages.
• Alerts from firewalls, IDS/IPS systems, endpoints, and servers.

Monitoring systems may use logs, flow records, SNMP, packet capture, endpoint telemetry, and other data sources. The best combination depends on the network and the available resources.

Explore network monitoring for more details.

Basic incident response steps

1. Identify and validate the alert or suspected security incident.
2. Determine which devices, accounts, and services may be affected.
3. Contain the incident using approved procedures and access controls.
4. Preserve relevant logs and evidence for investigation.
5. Remove the cause, remediate weaknesses, and restore systems safely.
6. Review the incident and improve controls to reduce recurrence.

Incident response should follow an organization's documented procedures. Avoid making changes that could destroy important evidence unless immediate containment is necessary.

Network security best practices

A practical network defense program starts with basic controls and improves over time.

• Maintain an asset inventory: Know which devices, operating systems, network services, and software versions are present.
• Patch regularly: Apply security updates to routers, switches, firewalls, access points, servers, and endpoints.
• Use strong authentication: Replace default credentials, enable multi-factor authentication where supported, and remove unused accounts.
• Limit access: Restrict administrative interfaces and allow only necessary services and connections.
• Secure Wi-Fi: Use modern encryption, strong credentials, updated firmware, and appropriate guest network separation.
• Enable logging: Collect relevant logs centrally when possible and protect them against unauthorized modification.
• Back up critical data: Keep protected backups and test restoration procedures.
• Review firewall rules: Remove unnecessary permissions and document important changes.
• Prepare for incidents: Establish response procedures and test them before an emergency.
• Use authorized testing: Assess only networks and systems you own or have explicit permission to test.

Related network security topics

Continue learning through these focused guides. Each page should explain its subject in more depth than this overview.

Frequently asked questions