It seems that by default, Google Cloud load balancers expose a number of ports unecessarily. I haven't found a way to expose only 80/443 and every time I make one of their load balancers, the following ports are seen in an nmap:
PORT STATE SERVICE 25/tcp open smtp 80/tcp open http 110/tcp open pop3 143/tcp open imap 443/tcp open https 465/tcp open smtps 587/tcp open submission 993/tcp open imaps 995/tcp open pop3s 1720/tcp open H.323/Q.931 8080/tcp open http-proxy
Is there a way to block 25, 465, 587, 993 & 995? Note that this question is aboout GCP load balancers, not firewalls.