If you’re managing linux servers (or desktops, even), I highly recommend this firewalling suite called CSF/LFD. Been using it for decades, and it has protected ‘my’ linux machines better than anything else ever could. Proud to say none of the systems I manage have been compromised, hacked, broken in to or ransomwared. CSF is easy to install and comprehend even for linux noobs, has well written documentation and does what you hope it does and usually better! It offers an integrated webserver user interface, or integrates in existing control panels (like webmin). And amazingly it’s still completely free!
I have not been paid for this. It’s just out of sheer appreciation and being thankful for all the hard work that its devs have put into it which made me decide to post this.