Network Security Fundamentals

Network security protects devices, data, users, and services. Even basic networks need security because attackers may attempt to steal information, disrupt services, or gain unauthorized access.

A threat is a potential danger. A vulnerability is a weakness that can be exploited. A mitigation is a control used to reduce risk.

Attackers may exploit weak passwords, outdated software, misconfigured devices, unprotected remote access, insecure wireless settings, or careless user behavior.

Common attack categories include:

Access attacks target accounts, passwords, devices, or services. Examples include password guessing, brute-force attempts, credential theft, privilege escalation, and exploiting unsecured management services.

Strong authentication, account lockout policies, least privilege, and secure management protocols help reduce access attack risk.

Effective security uses multiple layers.

Common mitigations include:

• Keep software and firmware updated.
• Use strong unique passwords.
• Disable unused services and ports.
• Use SSH instead of Telnet.
• Apply least privilege.
• Use firewalls and access control lists.
• Segment networks.
• Monitor logs and alerts.
• Back up important data.
• Train users to recognize social engineering.

AAA is a security framework.

AAA helps organizations control and record access to network devices and services.

A firewall filters traffic based on rules. It may allow, deny, inspect, or log traffic. Firewalls can protect the boundary between networks and can also segment internal networks.

Firewall rules may use source address, destination address, protocol, port, application, or connection state.

Endpoint devices such as laptops and phones are common targets. Endpoint security may include antivirus tools, host firewalls, operating system updates, disk encryption, device locking, and safe browsing practices.

Routers and switches should be hardened. Basic device hardening includes:

• Use strong passwords.
• Encrypt stored passwords where possible.
• Use SSH for remote management.
• Disable unused ports.
• Set login banners.
• Limit management access.
• Save configurations securely.
• Keep firmware updated.