Windows Defender bug may fill your hard drive with thousands of files

[hazelnut]

Quote

If you are using a device with Microsoft's Windows 10 operating system and Windows Defender as the default security solution, you may be impacted by a bug that is filling the hard drive with files.

Windows Defender puts thousands of files in the folder C:\ProgramData\Microsoft\Windows Defender\Scans\History\Store if a device is affected by the issue. More than 10,800 items were placed in the folder on a test system running Windows 10 version 20H2. Other users reported over 950,000 files over the course of a 24 hour period and 30 Gigabytes of storage occupied by the files. Most files are small in size, between 1 and 2 Kilobytes.

 

https://www.ghacks.net/2021/05/05/windows-defender-bug-may-fill-your-hard-drive-with-thousands-of-files/

[nukecad]

Haven't we seen that, or a similar, Defender logs bug before?

Just checked and It's made 184 entries in that directory so far today, and is creating more as I watch.
Most are 2KB but there is one from yesterday that's 2MB.
Look at the timestamps here:

 

I've updated Defender as suggested in that article, and deleted all those files and the directory is not filling up again.

It isn't a directory that CCleaner cleans by default so if you are affected, and it seem that many/most are, then you'll have to delete them manually.
 

[hazelnut]

Supposed to be a fix on the way according to the article.

[nukecad]

Just updating Defender fixed it for me.

The logfiles in the hidden folder still needed manually deleting though.

[Andavari]

I had 816 files in there using about 5MB. I just manually deleted all of it.

It's another reason that Nukecad and I noted in a topic from awhile ago why having Defender cleaners in winapp2.ini can be beneficial to removing allot of accumulation it builds up - but that particular folder isn't cleaned by any winapp2.ini entries to my knowledge.

Edit:
I'm submitting that folder location to winapp2.ini.

Edited May 5, 2021 by Andavari

[trium]

i have defender never used and nevertheless saved it some files in this folder. but only a few with 700 - 800 kb. some from 2015, 2016 and 2018. (w8.1)

[hazelnut]

If you cannot get the update for the Defender fix through Win Updates (keeps saying there was a problem and to retry) instead right-click on the Defender taskbar icon and select to update that way.

[nukecad]

Just to add that if/when you do delete all those files Defender will then think that it has never run a scan, and may prompt you to run one.