What Is a Firewall?
Firewalls protect computers, networks, and devices from malware and malicious attacks. They examine incoming and outgoing data packets for signs of threats, like viruses, phishing attempts, denial-of-service attacks, and remote logins. Harmful data is blocked before it can cause damage and unauthorized access is denied.
A firewall is a network device that controls and filters traffic between the internal network (like your office or home) and external systems and connections, such as the Internet. Firewalls can be hardware appliances, software based on individual computer devices, or a combination of both. Hardware firewalls usually operate at the network layer (Layer 3) and use filtering methods such as those based on IP addresses, ports, and protocols.
Most firewalls also offer other features to protect your organization. For example, many off-the-shelf firewalls ship with preconfigured rulesets to reduce setup time. The benefit of these is that they often take into account common threats and vulnerabilities, allowing you to immediately reduce the risk of attack.
Other security features include antimalware, web-filtering, and granular application control. Some firewalls use stateful inspection to monitor each packet of data as it passes through. It looks at each packet to see where it comes from, where it’s going, and what it’s trying to do and compares that to a list of known threats. It’s a bit like a guard at a gate checking to see where someone is coming from and where they’re going before admitting them.