I was taking a look into Computer Management->Users and found that SQL Server Express has created a lot of users for me.

Why? Is my system infected?

local users

The descriptions all say, "Local user account for execution of R scripts in SQL Server instance SQLEXPRESS".

  • 1
    Please take some time and go through your questions and mark the helpful answers as a courtesy to the people helping you.
    – eckes
    Commented Jan 23, 2020 at 22:28

2 Answers 2


Do you have installed the R- and Machine Learning services? According to the documentation below those are generated to run external scripts of those services in an isolated environment. So I would say they are normal if you install those components.

Those are part of the Advanced Services Variant of the SQL Express Edition.

From the documentation: Modify the user account pool for SQL Server machine learning

By default, the user account pool contains 20 user accounts. In most cases, 20 is more than adequate to support machine learning tasks, but you can change the number of accounts.

  • In a default instance, the individual accounts are named MSSQLSERVER01 through MSSQLSERVER20.
  • For a named instance, the individual accounts are named after the instance name: for example, MyInstanceName01 through MyInstanceName20.
  • Sadly the link now leads to a 404 :( Anyway, to change the user account pool run "SQL Server configuration manager", right click on "SQL Server Launchpad" -> Properties -> Advanced -> External Users Count
    – Joril
    Commented Sep 11, 2023 at 9:16

Open Windows Security log and filter it for Event ID 4720: A user account was created.

You'll found who, when and with what attributes has created these users.

  • It got an empty list, opening event viewer, went into "Windows Logs" and "Security", then I right clicked "Security" and clicked "Filter Current Log"... and put 4720 in the textbox saying <All Event IDs>. Commented Nov 9, 2017 at 8:46
  • It is. It enabled by default, but if it is I bet it would say ‚TRUSTED INSTALLER‘ ,)
    – eckes
    Commented Nov 9, 2017 at 8:47

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