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5.1.6 Ensure that Network Security Group Flow logs are captured and sent to Log Analytics (Manual)​

Profile Applicability​

• Level 2

Description​

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.

Audit​

From Azure Portal​

  1. Navigate to the Azure Monitor Blade
  2. Select Networks
  3. Select the Network Watcher option
  4. Then NSG Flow Logs
  5. For each log you wish to audit select it from this view.

Remediation​

From Azure Portal​

  1. Navigate to the Azure Monitor Blade
  2. Select Networking
  3. Select the Network Watcher option
  4. Then NSG Flow Logs
  5. Select + Create
  6. Select the desired Subscription.
  7. Select the + NSG and the network service group for a network.
  8. Select the Storage Account to log and the retention in days to retain the log.
  9. In Configurations keep the default value of v2. If you desire even further analysis select Enable Traffic Analytics, then the processing interval, and the Log Analytics Workspace.
  10. Tag as desired, then go to Create. Then 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.

References​

https://docs.microsoft.com/en-us/azure/network-watcher/network-watcher-nsg-flow-logging-portal
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-logging-threat-detection#lt-4-enable-network-logging-for-security-investigation