I configured my server to block all ports except 22,80 and 443 with UFW. I then created a fail2ban rule to put in jail every IP that scan ports unsuccessfully more than 5 times and report it to AbuseIP.
After some adjustments it's working well so far, except that I noticed my port 27015 is reported a lot of times with IPs that I seem to be the only one to report, for example: https://www.abuseipdb.com/check/72.76.108.239
What do you think might lead to this? I suspect the previous owner of the server used it for some steam game servers, but I can't be sure.