What a firewall actually does

The basic job

A firewall sits between your network and the internet and decides what traffic may pass. By default it lets your staff reach out to the internet and blocks unrequested traffic coming in.

Modern business firewalls do more:

• Filter websites known to be malicious.
• Inspect traffic for known attacks.
• Separate internal networks, such as guest Wi-Fi, from business systems.
• Provide remote access for staff working elsewhere.

Why firewalls are a target

The firewall faces the internet all day, every day, so attackers scan for firewalls with known flaws. Remote-access features on firewalls are among the most common ways into a business network. Several of the flaws on the US government’s list of actively exploited vulnerabilities each year are in firewalls and remote-access devices.

Keeping it healthy

• Update the firmware when fixes are released, promptly for security fixes.
• Use multi-factor authentication for remote access through it.
• Review the rules. Exceptions added years ago for a vendor or an old system are often still open.
• Replace it before the manufacturer stops releasing updates.