# Security Group A group of rules that apply to inbound and outbound network traffic for a VM. A security group acts as a virtual firewall that controls the inbound and outbound network traffic for the VMs to which the group has been assigned. Rules are defined based on what type of network traffic should be allowed to the VM 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 that allows all outbound traffic from the VM to which the security group has been assigned. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.platform9.com/private-cloud-director/virtualized-networking/security-group.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.