Microsoft fixes Windows 10 Defender bug generating thousands of files

According to user reports and our tests,
Windows Defender is dropping thousands of files on the
system drive of Windows 10. The problem has been widely
reported by users who have discovered that a faulty Windows
Defender update is responsible for the mess.

Microsoft Defender comes pre-installed on all versions/editions
of Windows 10 and is updated regularly via Windows Update.
Following a recent update to Windows Defender in the last week
of April, users noticed that Windows has started generating
thousands of files in the system drive i.e the location where
the operating system is installed.

Affected users reported on Microsoft forums
and Reddit
that their Windows Defender history folder
(C:ProgramDataMicrosoftWindows DefenderScansHistoryStore)
quietly filed up with files. The files themselves are tiny and
harmless, but they can consume a massive amount of storage
space in some cases.

Windows Defender bug

The bug is also hitting Windows Server installations, with some
people reporting that it generated 18 million files in their

“We have three 2016 servers so far that are affected. Our
alerts for HDD space started going off last night. One server
has 18 MILLION FILES in the Store folder. Another has 13
MILLION. Taking hours just to discover all of the files so that
they can be deleted. And due to the allocation size, these
files are taking up 50-60GB of space on the disk. This is a
major screw up from Microsoft,” a user noted on

How to check if Windows Defender is generating files

The easiest way to check if Windows Defender is plagued with
the bug is through File Explorer:

  • Open File Explorer and make sure “Hidden items” are allowed
    on the View tab.
  • In the address bar, type “C:ProgramDataMicrosoft”
    without the quotation marks.
  • Click on “Windows Defender”.
  • Click on “Continue” if the folder requests administrator
  • In the Windows Defender folder, navigate to

If you’re affected, you will see hundreds or thousands of files
with less than one megabytes size each. You can safely
delete the files that are in the folder.

Windows Defender version 1.1.18100.6 has fixed the issues

The good news is that the problem appears to have been resolved
with Windows Defender engine 1.1.18100.6. A Microsoft support
agent also told us that they’re aware of the reports and fix is
being deployed.

To apply the patch, open the Start Menu and click on the
Settings cog icon. In the Settings app, navigate to Updates &
Security > Windows Update and click on check for updates.

A new update titled “Security Intelligence Update for Microsoft
Defender Antivirus” will automatically start downloading and

You can verify the version number of the security engine by
opening the ‘About’ page in Windows Security app.

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