Default Security Group and Rules

Note the following when using default security group rules:

Inbound rules control incoming traffic to instances in the default security group. The instances can only communicate with each other but cannot be accessed from external networks.
Outbound rules allow all traffic from the instances in the default security group to external networks.

Figure 1 shows the default security group.

Figure 1 Default security group
Click to enlarge

Both default and custom security groups are free of charge. The name of a default security group is default.
You cannot delete the default security group, but you can modify existing rules or add rules to the group.
The default security group is automatically created to simplify the process of creating an instance for the first time. The default security group denies all external requests. To log in to an instance, add a security group rule by referring to Remotely Logging In to an ECS from a Local Server.

Table 1 describes the rules in the default security group.

**Table 1** Rules in the default security group
Direction	Action	Type	Protocol & Port	Source/Destination	Description
Inbound	Allow	IPv4	All	Source: default security group (default)	This rule allows IPv4 instances in the security group to communicate with each other using any protocol over any port.
Inbound	Allow	IPv6	All	Source: Default security group (default)	This rule allows IPv6 instances in the security group to communicate with each other using any protocol over any port.
Outbound	Allow	IPv4	All	Destination: 0.0.0.0/0	This rule allows all traffic from the instances in the security group to any IPv4 address over any port.
Outbound	Allow	IPv6	All	Destination: ::/0	This rule allows all traffic from the instances in the security group to any IPv6 address over any port.

When you create an ECS for the first time, the system automatically creates a VPC vpc-default and:

**Table 2** Default security group rules
Direction	Action	Type	Protocol & Port	Source/Destination	Description
Inbound	Allow	IPv4	TCP: 3389	Source: 0.0.0.0/0	Allows all IPv4 addresses to access Windows ECSs through the default Windows remote desktop.
Inbound	Allow	IPv4	TCP: 22	Source: 0.0.0.0/0	Allows all IPv4 addresses to access Linux ECSs over SSH.
Inbound	Allow	IPv4	All	Source: Default security group (default)	Allows instances in the security group to communicate with each other over IPv4 protocols.
Inbound	Allow	IPv6	All	Source: Default security group (default)	Allows instances in the security group to communicate with each other over IPv6 protocols.
Outbound	Allow	IPv4	All	Destination: 0.0.0.0/0	Allows access from instances in the security group to any IPv4 address over any port.
Outbound	Allow	IPv6	All	Destination: ::/0	Allows access from instances in the security group to any IPv6 address over any port.

**Table 3** Sys-WebServer security group rules
Direction	Action	Type	Protocol & Port	Source/Destination	Description
Inbound	Allow	IPv4	ICMP: All	Source: 0.0.0.0/0	Allows to use the ping command to test the network connectivity over IPv4 protocols.
Inbound	Allow	IPv4	All	Source: current security group (Sys-WebServer)	Allows instances in the security group to communicate with each other over IPv4 protocols.
Inbound	Allow	IPv4	TCP: 443	Source: 0.0.0.0/0	Allows all IPv4 addresses to access websites deployed on ECSs over HTTPS.
Inbound	Allow	IPv4	TCP: 80	Source: 0.0.0.0/0	Allows all IPv4 addresses to access websites deployed on ECSs over HTTP.
Inbound	Allow	IPv4	TCP: 22	Source: 0.0.0.0/0	Allows all IPv4 addresses to access Linux ECSs over SSH.
Inbound	Allow	IPv4	TCP: 3389	Source: 0.0.0.0/0	Allows all IPv4 addresses to access Windows ECSs through the default Windows remote desktop.
Inbound	Allow	IPv6	All	Source: current security group (Sys-WebServer)	Allows instances in the security group to communicate with each other over IPv6 protocols.
Outbound	Allow	IPv4	All	Destination: 0.0.0.0/0	Allows access from instances in the security group to any IPv4 address over any port.
Outbound	Allow	IPv6	All	Destination: ::/0	Allows access from instances in the security group to any IPv6 address over any port.

**Table 4** Sys-FullAccess security group rules
Direction	Action	Type	Protocol & Port	Source/Destination	Description
Inbound	Allow	IPv4	All	Source: current security group (Sys-FullAccess)	Allows instances in the security group to communicate with each other over IPv4 protocols.
Inbound	Allow	IPv6	All	Source: current security group (Sys-FullAccess)	Allows instances in the security group to communicate with each other over IPv6 protocols.
Inbound	Allow	IPv4	All	Source: 0.0.0.0/0	Allows all inbound data packets to pass through over IPv4 protocols.
Inbound	Allow	IPv6	All	Source address::/0	Allows all inbound data packets to pass through over IPv6 protocols.
Outbound	Allow	IPv4	All	Destination: 0.0.0.0/0	Allows access from instances in the security group to any IPv4 address over any port.
Outbound	Allow	IPv6	All	Destination: ::/0	Allows access from instances in the security group to any IPv6 address over any port.