Preserve ATA investigation data and document exclusions before migration

Use this document to resolve one bounded operational decision: Preserve ATA investigation data and document exclusions before migration. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official Migrate from Advanced Threat Analytics to Microsoft Defender for Identity from Microsoft supports the following bounded statements:

• ATA data is not migrated to Defender for Identity, so Microsoft recommends retaining the ATA Data Center and alerts needed for ongoing investigations until those alerts are closed or remediated. The research record locates this support at Migration comparison > Important note before Prerequisites.
• ATA alert exclusions are not transferable; their details must be collected so the exclusions can be recreated in Microsoft Defender. The research record locates this support at Plan your migration > Alert exclusions.
• The ATA Center must remain installed until all ATA Gateways are removed because removing the center while gateways still run leaves no threat protection. The research record locates this support at Plan your migration > Caution.

Only the traced statements above are asserted as source facts. Apply the review to Defender for Identity workspaces, sensors, directory-service accounts, action accounts, network paths, roles, and deployment health after confirming that the source and deployed context match.

What the source does not establish

This migration guide covers Defender for Identity sensors, not standalone sensors; preserve evidence and verify current product support rather than treating migration as an in-place data transfer. The citation is not a substitute for observed state, authorization, compliance evidence, or dependency health. Examine Active Directory, Windows DNS, time, certificates, domain-controller resources, network capture, cloud connectivity, and security operations before translating the source into an operational decision.

Applicability questions

• For source statement 1 at Migration comparison > Important note before Prerequisites, which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Plan your migration > Alert exclusions, which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Plan your migration > Caution, which observable configuration, record, or test can confirm applicability here?
• What inventory proves which parts of Defender for Identity workspaces, sensors, directory-service accounts, action accounts, network paths, roles, and deployment health are in and out of scope?
• Which condition in Active Directory, Windows DNS, time, certificates, domain-controller resources, network capture, cloud connectivity, and security operations must be healthy before evidence is trustworthy?
• What result would disprove the working assumption and return the issue to the owner?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Begin by recording scope and current state before deciding whether a change is warranted. Record the source location, examined part of Defender for Identity workspaces, sensors, directory-service accounts, action accounts, network paths, roles, and deployment health, observed and expected states, owner, and reason for deviation.

Translate the conclusion into change control only after documenting dependencies, impact, test method, expected signals, failure signals, and restoration steps. Include Active Directory, Windows DNS, time, certificates, domain-controller resources, network capture, cloud connectivity, and security operations, while excluding secrets and sensitive personal or topology data from ordinary tickets.

Verification and evidence

Keep the source locations Migration comparison > Important note before Prerequisites; Plan your migration > Alert exclusions; Plan your migration > Caution adjacent to the sanitized artifacts used for comparison. Prefer sensor inventory, service and action-account permissions, health alerts, connectivity tests, portal state, and controlled detection tests, with enough identity and timing data for an independent recheck.

Record the decision even when no change is made, including uncertainty and the next trigger. Use safe testing conditions for disruptive work, preserve rollback proof, and revisit the conclusion after relevant platform, dependency, vendor, or ownership changes.

Official references

• Migrate from Advanced Threat Analytics to Microsoft Defender for Identity — Microsoft