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Source facts

\n

Microsoft says virtual-network flow logs append blocks to a block blob at one-minute intervals. It warns against editing, overwriting or deleting the blob contents during ingestion because changing the block structure can cause later writes to that hour’s blob to fail. The guidance also cautions against modifying Traffic Analytics-managed collection resources. Microsoft Learn.

\n

Applicability

\n

Apply this review to evidence collection, troubleshooting scripts and storage maintenance touching active flow-log data. Identify the live writer, current blob and any service-managed collection objects before running a cleanup or transformation.

\n

DSE recommendation

\n

DSE recommends working from a separate read-only acquisition for analysis. Document the source artifact, collection time and destination copy, and keep transformations away from the active writer. Review maintenance jobs for operations that modify blob contents. Escalate collection-resource changes to the monitoring owner rather than treating those objects as unused infrastructure.

\n

Verification

\n

Check that new flow records continue arriving through the collection period. Preserve acquisition metadata and compare the observed timeline with expected ingestion. If an active blob was modified, record the affected interval and investigate missing records before relying on that hour’s log as complete evidence.

\n

Official references

\n

Microsoft Learn: Manage Virtual Network Flow Logs.

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Escalate collection-resource changes to the monitoring owner rather than treating those objects as unused infrastructure.\nVerification\nCheck that new flow records continue arriving through the collection period. Preserve acquisition metadata and compare the observed timeline with expected ingestion. If an active blob was modified, record the affected interval and investigate missing records before relying on that hour’s log as complete evidence.\nOfficial references\nMicrosoft Learn: Manage Virtual Network Flow Logs.", "content_markdown": "## Source facts\n\nMicrosoft says virtual-network flow logs append blocks to a block blob at one-minute intervals. It warns against editing, overwriting or deleting the blob contents during ingestion because changing the block structure can cause later writes to that hour’s blob to fail. The guidance also cautions against modifying Traffic Analytics-managed collection resources. [Microsoft Learn](https://learn.microsoft.com/en-us/azure/network-watcher/vnet-flow-logs-manage).\n\n## Applicability\n\nApply this review to evidence collection, troubleshooting scripts and storage maintenance touching active flow-log data. Identify the live writer, current blob and any service-managed collection objects before running a cleanup or transformation.\n\n## DSE recommendation\n\nDSE recommends working from a separate read-only acquisition for analysis. Document the source artifact, collection time and destination copy, and keep transformations away from the active writer. Review maintenance jobs for operations that modify blob contents. Escalate collection-resource changes to the monitoring owner rather than treating those objects as unused infrastructure.\n\n## Verification\n\nCheck that new flow records continue arriving through the collection period. Preserve acquisition metadata and compare the observed timeline with expected ingestion. 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