Create a security group

A security group functions as a virtual firewall to control network access of Elastic Compute Service (ECS) instances. Each instance must belong to at least one security group. This topic describes how to create a security group and configure security group rules in the ECS console.

1. Go to the Security Groups page.
   1. Log on to the ECS console.
   2. In the left-side navigation pane, choose Network & Security > Security Groups.
   3. In the top navigation bar, select a region.
2. Click Create Security Group.
3. In the Basic Information section, set the parameters for the security group.

   Parameter	Description
   Security Group Name	Specify a security group name.
   Description	Enter a brief description of the security group for future management.
   Network	Set the network type of the security group. To create a VPC-type security group, select an existing VPC. To create a classic network-type security group, select Classic Network.
   Security Group Type	Select a security group type. Basic Security Group: applicable to scenarios with small-scale clusters and moderate network connections. Advanced Security Group: applicable to scenarios with large-scale clusters that require highly efficient O&M. For other functional differences between basic and advanced security groups, see Overview.
   Resource Group	Select a resource group to which to assign the security group to facilitate subsequent O&M.
   Tags	Configure tags for the security group to facilitate subsequent O&M.

4. Optional: In the Access Rule section, configure the security group rule.
   The system configures a default security group rule that has the basic configurations. If you want to make custom configurations, you can perform the following operations. For more information, see Add security group rules.
   1. Click the Inbound or Outbound tab to select the security group rule direction.

      Network type	Rule direction
      VPC	Inbound: controls inbound traffic from both the Internet and internal network. By default, the inbound rules are configured for the ICMP protocol, SSH port 22, RDP port 3389, HTTP port 80, and HTTPS port 443. Outbound: controls outbound traffic to both the Internet and internal network. By default, all ports are enabled to allow outbound access of basic security groups, and all ports are disabled to deny outbound access of advanced security groups.
      Classic network	Internet Ingress: By default, the inbound rules are configured for the ICMP protocol, SSH port 22, RDP port 3389, HTTP port 80, and HTTPS port 443. Internet Egress: By default, all ports are enabled. Inbound: By default, all ports are disabled to deny inbound access over the internal network. Outbound: By default, all ports are enabled to allow outbound access over the internal network.

   2. Click Add Rule.
   3. Configure custom security group rules.

      Parameter	Description
      Action	Allow: allows access requests on the specified port. Forbid: discards data packets and returns no messages. If two security group rules differ only in their actions, the Forbid rule is used but the Allow rule is ignored.
      Priority	A smaller value indicates a higher priority. Valid values: 1 to 100.
      Protocol Type	The protocol type of the security group rule. Valid values: All Custom TCP Customized UDP All ICMP (IPv4) All GRE For more information about the Protocol Type and Port Range parameters, see Add security group rules and Common ports used by applications.
      Port Range	You can specify a custom port range when Protocol Type is set to Custom TCP or Customized UDP. Enter one or more port ranges. Separate multiple port ranges with commas (,). Example: 22/23,443/443.
      Authorization Object	You can set the following authorization objects: IP addresses You can enter a single IP address. Example: 192.168.0.100. CIDR blocks You can enter a CIDR block. Example: 192.168.0.0/24. For more information about the CIDR format, see What is CIDR? Security groups This authorization type is valid only for the internal network. You can specify a security group within the current account or a different account as the authorization object to control access to or from the instances in that security group for the instances in the current security group. Note For advanced security group rules, you cannot select a security group for Authorization Object. Authorize a security group within the current account: Enter the ID of the security group that you want to authorize within the current account. If the current security group is of the VPC type, the security group that you want to authorize must reside in the same VPC as the current security group. Authorize a security group within a different account: Enter the ID of the different Alibaba Cloud account and the ID of the security group that you want to authorize in the ID of the Alibaba Cloud account/ID of the security group format. You can choose Account Management > Security Settings to view your account ID. Take note of the following items: You can enter up to 10 authorization objects at a time. Separate multiple objects with commas (,). If you enter 0.0.0.0/0 as an authorization object, all IP addresses are allowed or denied based on the Action parameter. Evaluate the network risks before you specify 0.0.0.0/0. For security reasons, we recommend that you select a security group for Authorization Object when you add an internal inbound rule to a security group of the classic network type. If you want to authorize IP addresses, you can enter only a single IP address. You cannot enter CIDR blocks.
      Description	The description of the security group rule.

5. Click Create Security Group.

Result

After the security group is created, it is displayed in the security group list.