Personal Firewall Day

What the day is

Personal Firewall Day is observed on January 15. It dates from an era when a home computer connected directly to the internet was genuinely exposed, and the advice has aged in an interesting way.

Origin and background

A firewall controls which network connections are allowed in and out of a machine. In the early 2000s that mattered enormously, because a freshly installed computer plugged into a broadband line was reachable from anywhere on the internet, with network services listening and unpatched. Machines were compromised within minutes of connecting, before the user could download the update that would have protected them. Worms spread across the internet in hours by scanning for exactly those open ports.

That specific problem is now largely solved, and mostly not by personal firewalls. Home routers perform network address translation, which means incoming connections have nowhere to go unless deliberately forwarded, and every mainstream operating system now ships with its firewall enabled and far fewer services listening by default.

The attacks moved accordingly. Almost nothing now arrives by knocking on a port. It arrives because somebody was persuaded to click, install, or type a password into a convincing page, and a firewall does not inspect intent. It permits the connection the user asked for.

So the day's advice still holds and no longer suffices. Leave the firewall on, and understand that the perimeter is no longer where the risk is.

How to take part

• Check your operating system firewall is actually on. It usually is, and it takes a minute to confirm.
• Change the router's default administrator password, which many households never do.
• Check whether anything is port-forwarded on your router and remove what you do not recognize.
• Apply pending updates, which does more than any firewall setting.
• Treat unexpected messages creating urgency as the actual modern threat.