Usually, you can check the DDI software version in the web console going to Help > About.

However, when you apply a Patch or Hotfix on the software, this major version display is not changed. Instead, you can check if they are applied successfully by going to Administration > Updates > Product Updates > Hot Fixes / Patches. This shows the Patch or Hotfix application history similar to the image shown below.

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For more detailed steps on how to apply Patch or Hotfix on DDI, refer to the Administrator's Guide (Chapter 6: Administration > Update > Product Updates) which is in the Online Help Center.

Furthermore, upon connecting your DDI to Trend Vision One, you can access this information in the Trend Vision One console. Simply, logon to Trend Vision One console: https://portal.xdr.trendmicro.com, go to NETWORK SECURITY OPERATONS > Network Inventory > Deep Discovery Inspector Appliances tab, click your DDI appliance. The Appliance Details page will display the detailed version, similar to the image shown below.

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Reference: Configuring Deep Discovery Inspector (DDI) to integrate with Trend Micro Vision One using Network Inventory Service