After importing a WSL distribution and copying files from one WSL instance to another, I ended up with thousands of files with :Zone.Identifier at the end of their names. Zone.Identifier is a Windows security metadata stream that marks files downloaded from the Internet.

Linux and WSL don’t support NTFS Alternate Data Streams, so this metadata appears as separate files when data is copied between environments.

The content of these files was like this

[ZoneTransfer]
ZoneId=3   ← Internet

How to delete them in WSL

You can safely remove all Zone.Identifier files directly from WSL using: 

find . -name '*:Zone.Identifier' -delete

Is it safe?

Yes — these files contain no real data and are used only by Windows to show security warnings.

Deleting them does not affect your project or source files.