Information
Network Security Group Flow Logs should be enabled and the retention period set to greater than or equal to 90 days.
Rationale:
Flow logs enable capturing information about IP traffic flowing in and out of network security groups. Logs can be used to check for anomalies and give insight into suspected breaches.
Impact:
This will keep IP traffic logs for longer than 90 days. As a level 2, first determine your need to retain data, then apply your selection here. As this is data stored for longer, your monthly storage costs will increase depending on your data use.
Solution
From Azure Portal
Go to Network Watcher
Select NSG flow logs blade in the Logs section
Select each Network Security Group from the list
Ensure Status is set to On
Ensure Retention (days) setting greater than 90 days
Select your storage account in the Storage account field
Select Save
From Azure CLI
Enable the NSG flow logs and set the Retention (days) to greater than or equal to 90 days.
az network watcher flow-log configure --nsg <NameorID of the Network Security Group> --enabled true --resource-group <resourceGroupName> --retention 91 --storage-account <NameorID of the storage account to save flow logs>
Default Value:
By default, Network Security Group Flow Logs are disabled.