Description:

Diagnostic Logs capture activity to the data access plane while the Activity log is a subscription-level log for the control plane. Resource-level diagnostic logs provide insight into operations that were performed within that resource itself, for example, getting a secret from a Key Vault. Currently, 32 Azure resources support Diagnostic Logging (See the references section for a complete list), including Network Security Groups, Load Balancers, Key Vault, AD, Logic Apps and CosmosDB. The content of these logs varies by resource type. For example, Windows event system logs are a category of diagnostics logs
for VMs, and blob, table, and queue logs are categories of diagnostics logs for storage accounts.

A number of back-end services were not configured to log and store Diagnostic Logs for certain activities or for a sufficient length. It is crucial that logging systems are correctly configured to log all relevant activities and retain those logs for a sufficient length of time. By default, Diagnostic Logs are not enabled. Given that the mean time to detection in an enterprise is 240 days, a minimum retention period of two years is recommended.

Note: The CIS Benchmark covers some specific Diagnostic Logs
separately.

3.3 - Ensure Storage logging is enabled for Queue service for read, write, and delete requests

6.4 Ensure that Network Security Group Flow Log retention period is 'greater than 90 days'

Rationale:

A lack of Diagnostic Logs reduces the visibility into the data plane and therefore an organization's ability to detect reconnaissance, authorization attempts or other malicious activity. Unlike Activity Logs, Diagnostic Logs are not enabled by default. Specifically, without Diagnostic Logs it would be impossible to tell which entities had accessed a data store that
which was breached. In addition, alerts for failed attempts to access APIs for Web Services or Databases are only possible
when Diagnostic Logging is enabled.

Costs for Log Analytics Workspaces varies with Log Volume. Not every resource need to have logging enabled. It's important to determine the security classification of the data being processed by the given resource and adjust the logging based on which events need to be tracked. This is typically determined by governance and compliance requirements.

ID	Name	CSP	Domain	Severity
AC_AZURE_0210	Ensure that Diagnostic Logs Are Enabled for All Services that Support it	Azure	Logging and Monitoring	MEDIUM
AC_AZURE_0216	Ensure that a 'Diagnostics Setting' exists	Azure	Logging and Monitoring	MEDIUM
AC_AZURE_0242	Ensure Diagnostic Setting captures appropriate categories	Azure	Logging and Monitoring	MEDIUM

Detections

Analytics

Tenable Cloud Security Policies Search

MEDIUM

MEDIUM

MEDIUM