AWS VPC Flow Logs can help you keep better track of IP traffic between network interfaces on your Amazon Virtual Private Cloud. It’s particularly useful for maintenance and auditing of your traffic and permissions. It can help monitor and identify traffic coming in and out of your VPC instances, and keep tabs on the users and groups that access them.
See which port the source and destination were using.
Packets and bytes transferred
Keep an eye out for suspicious or unnecessary data.
Find out whether actions were accepted or rejected by the security systems.