How can you prevent your firewall from becoming a vulnerability?

"Welcome back! Today let's talk about firewalls.
"Everybody has them, everybody needs them - as a business it's critical, right?
But it sits there, and the problem is is a lot of people don't always review their firewalls.
"They set it and forget it, and firewalls are not that kind of appliance.
"You need to maintain your firewall. Make sure that you're reviewing your firewall rules, so that there's no vulnerabilities.
"Let's say you had a firewall rule set up to go to a server. You decommission that server, but your firewall rule is still there, which opens a vulnerability to your network.
"So you always want to make sure that you're reviewing those periodically, especially if you make any changes, or if anything recently has happened or updated.
"Also, firewalls usually have a subscription, and you always want to make sure that subscription is updating and running correctly.
"That's really what helps keep the bad guys out.
"Periodically, make sure you're checking that your rules are up to date and that your subscriptions are functioning.
"That's it for today - talk to you next week."