As I mentioned in this post, a security group is similar to virtual firewalls and is used to set network access controls for one or more ECS instances.
By default, Alibaba Cloud system will create rules for ICMP ports, TCP Port 22 and TCP Port 3389 automatically. These default security group rules were not well thought out.
As I created a Linux instance, the inbound security group rule of 3389 shouldn’t exist. You should remove all unnecessary security group rules aka firewall rules.
Also, I’m planning to configure a secure web server, therefore a port 443 security group rule is needed.