A security group is a group of rules that apply to inbound and outbound network traffic for an instance. A security group acts as a virtual firewall that controls the inbound and outbound network traffic for the instances to which the group has been assigned.
Rules are defined based on what type of network traffic should be allowed to the instance to which the security group is assigned. Traffic that does not match any of the rules assigned to an instance, is denied access, by default.
A default rule is predefined in Clarity that allows all outbound traffic from the instance to which the security group has been assigned.