5.1.6 Ensure that Network Security Group Flow logs are captured and sent to Log Analytics

Information

Ensure that network flow logs are captured and fed into a central log analytics workspace.

Rationale:

Network Flow Logs provide valuable insight into the flow of traffic around your network and feed into both Azure Monitor and Azure Sentinel (if in use), permitting the generation of visual flow diagrams to aid with analyzing for lateral movement, etc.

Impact:

The impact of configuring NSG Flow logs is primarily one of cost and configuration. If deployed, it will create storage accounts that hold minimal amounts of data on a 5-day lifecycle before feeding to Log Analytics Workspace. This will increase the amount of data stored and used by Azure Monitor.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

From Azure Portal

Navigate to Network Watcher.

Select NSG flow logs.

Select + Create.

Select the desired Subscription.

Select + Select NSG.

Select a network security group.

Click Confirm selection.

Select or create a new Storage Account.

Input the retention in days to retain the log.

Click Next.

Under Configuration, select Version 2.

If rich analytics are required, select Enable Traffic Analytics, a processing interval, and a Log Analytics Workspace.

Select Next.

Optionally add Tags.

Select Review + create.

Select Create.

Warning
The remediation policy creates remediation deployment and names them by concatenating the subscription name and the resource group name. The MAXIMUM permitted length of a deployment name is 64 characters. Exceeding this will cause the remediation task to fail.

Default Value:

By default Network Security Group logs are not sent to Log Analytics.

See Also

https://workbench.cisecurity.org/benchmarks/10624