Network Security Measures

After learning about the threats that networks face, this lesson covers the security measures used to protect networks, data and users. A layered approach — using multiple defences together — provides the strongest protection.

---

Firewalls

A firewall is a security system that monitors and controls incoming and outgoing network traffic based on a set of predefined rules. It acts as a barrier between a trusted internal network and an untrusted external network (such as the internet).

How firewalls work

• A firewall examines each packet of data entering or leaving the network.
• It checks the packet against its rules (also called policies or access control lists).
• Packets that match an "allow" rule are permitted through; packets that match a "deny" rule are blocked.
• Rules can be based on: IP addresses, port numbers, protocols and packet content.

Types of firewall

Type	Description
Hardware firewall	A dedicated physical device placed between the internal network and the internet. Common in businesses.
Software firewall	A program running on a computer (e.g. Windows Firewall). Protects individual devices.

What firewalls can do