What Is a Firewall?
A firewall is a device that limits network access and protects from internal and external threats. Firewalls can be physical or software.
A hardware firewall is a physical device that stores between your gateway and the internet, while a software firewall is an internal program on your computer that works through port numbers and applications. They both provide a first line of defense and can help prevent malicious traffic from infecting other devices in your network.
Packet filtering firewalls use OSI layers 3 and 4 to scan traffic in your network for threats. If a packet does not meet predetermined criteria, it’s rejected and blocked.
Circuit-level gateways verify transmission control protocol (TCP) handshakes to identify whether a packet is from a legitimate session or not. This is a simple but efficient form of protection that’s designed to quickly approve or deny incoming data without using large computing resources.
Stateful multilayer inspection firewalls (SMLI) examine packets in their context as they travel throughout your network. They can be especially helpful for detecting malware and outgoing data that could pose a security risk.
Proxy server: These servers act as proxy* servers, capturing and filtering data between your computer and a remote IP address. They’re a key part of unified threat management and often work alongside sandboxing and traffic validation capabilities to filter out malware, dangerous website content, and other harmful data that might pass through your network.
A network firewall, also known as a perimeter-based firewall, is installed at the perimeter of your organization’s network to create an extra layer of security. They monitor traffic at OSI Layers 3 and 4 for threats, and they perform deep packet inspection to check incoming and outgoing packets against predetermined criteria.