Every connection passing through is compared against the rules: where it comes from, where it is going, and which service it uses. By default a business firewall blocks unrequested traffic from the internet and permits connections that staff start. Modern business firewalls, often called next-generation firewalls, also inspect traffic for known attacks, filter websites, provide VPN access, and control traffic between internal VLANs.
The router supplied by an internet provider offers basic protection but little control or visibility. A business firewall lets a company decide what is allowed, separate guests and smart devices from business systems, give remote staff secure access, and keep logs that show what happened during an incident. Firewalls are one of the five control areas in the UK Cyber Essentials scheme.
A firewall is only as good as its configuration and upkeep. Common weaknesses are default admin passwords, management pages reachable from the internet, old rules nobody remembers adding, and firmware left unpatched. Security features that rely on a subscription stop updating when it lapses. A firewall also cannot protect laptops once they leave the office. We install, configure, and maintain firewalls as part of our network and security services.