The firewall is your network's border control. With clear rules, segmentation and maintenance it offers solid protection even without specialist knowledge.
A firewall filters traffic between networks according to rules: who may talk to whom, over which port, in which direction. Modern devices ("next-generation") add application detection, intrusion prevention and content filtering.
Basic rules
Deny by default: only allow connections that are explicitly needed.
Keep inbound minimal: no unnecessary exposure to the internet; remote access through VPN.
Segment the network: separate office, guests, servers and devices and regulate transitions.
Document rules and clean them up regularly: old exposures are common weaknesses.
Keep firmware current and secure administration (MFA, no access from the internet).
Review logs: spot anomalies.
Typical mistakes
Port forwards for remote desktop set up "just briefly" and never removed; default passwords; a flat network without separation; firmware never updated. A half-yearly rule review avoids most of these problems.
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Frequently asked questions
Does a small company need a firewall?
Yes. It is the central control point between the internet and the company network. Router firewalls too must be configured cleanly and kept current.
What is a next-generation firewall?
A firewall with additional functions such as application detection, intrusion detection and content filtering.
How often should firewall rules be reviewed?
At least every six months and with every change to the infrastructure.