Reproduction steps:

1. Create a New Project
2. In the "Assets" folder, create a New Folder and change its icon ("Right Click" -> "Properties" -> "Customize" -> "Change Icon" -> Change to any icon)
3. Observe that Windows has created a special file "desktop.ini"
4. Focus the Editor window
5. Unity incorrectly imports the "desktop.ini" file and creates a "desktop.ini.meta" file

Expected Result: Windows created special files like "desktop.ini" should be ignored and should not be imported
Actual Result: Editor imports Windows created special files and creates a meta file

Reproduced with: 2019.1.0a11, 2018.3.0b12, 2018.2.18f1, 2018.1.9f2, 2017.4.16f1

Note:
Add this type of files to the "Hidden Assets" which are ignored by Unity (https://docs.unity3d.com/Manual/SpecialFolders.html - Hidden Assets)
"This is used to prevent importing special and temporary files created by the operating system or other applications."