UPDATED March 24: There is a way to prevent this annoying message from appearing, but please be patient. See below.

UPDATED March 30: Microsoft has fixed this issue in an out-of-band Windows Update release. See below.

Windows Defender, the anti-malware component of Windows 10, is skipping files during security scans for no apparent reason for many users.

According to Bleeping Computer, a number of Windows 10 users have reported receiving the message "Items skipped during scan" even though they have not set file exclusion in Windows Defender preferences.

When users perform either a quick scan or a full scan, an Action Center notification may be generated stating that items were skipped during the scan "due to exclusion or network scan settings."

Windows Defender can be assigned to skip or exclude certain files on a device during a scan. However, if no exclusions are assigned, all files should be evaluated by Defender when a malware scan is initiated. However, this is not the case.

BleepingComputer was able to reproduce this message while running a malware scan on Windows 10. However, we found a discrepancy in the version of Windows Defender Antimalware Client with which this issue was reported.

Bleeping Computer also stated that this error does not affect all Windows Defender users, but rather those using the same Windows Defender engine version. German technology blogger Guenter Born, who reported the problem a few days ago, told Bleeping Computer that about 20% of his readers said they had no problems, but 80% did.

The problem may have started with the Windows March patch released on March 10, 2020. However, since Microsoft has not acknowledged the problem, it is unclear what is causing the error and whether it is being addressed.

A Reddit thread discussing the issue began on March 10, and there have been several threads on Microsoft's user forums.

Although Windows 10 could be rolled back before the March security patch, we do not recommend it because Microsoft fixed many critical flaws in that update. Instead, we recommend using the best antivirus program for your computer until Microsoft resolves the Windows Defender issue.

Later, on March 23, Born reported, and Bleeping Computer confirmed, that the problem is a network scan that is disabled in Windows Defender--that is, a network scan that is not directly on the computer, but is a local network files that are not directly on the computer but are linked to it via the local network.

Ironically, Microsoft recommends that network scanning be disabled by default. This is because scanning all accessible files on a network device takes much longer and consumes much more processing power than scanning the system's own drives.

As one of Born's readers pointed out, you also don't want multiple machines on the same local network scanning each other's files at the same time, resulting in slower network traffic.

However, it appears that someone preparing an update for the March 2020 Patch Tuesday update did not receive this memo. That is not true.

If you are really concerned about the "items skipped during scan" notification, log in as administrator, open Windows PowerShell and type:

Set-MpPreference -Di sableScanningNetworkFiles 0

... and press Enter. (The text string ends with a "0" instead of an "O". Zero, so to speak, disables the override; typing "1" turns the override back on.)

Still, Born recommends that until Microsoft resolves this minor issue, do not enable network scanning and live with the "item was skipped" notification. At least you know that this notification is not serious.

UPDATE March 30: Microsoft has permanently fixed this issue in an out-of-band security update. This update may affect how AppLocker updates applications and may also block the startup of some computers that have SecureBoot enabled. (Many computers have SecureBoot turned on at the factory.)