Alternate Data Streams can be used to hide files in NTFS disk system like Windows 10.
notepad a.txt
a.txt ==================
I am Leo
Hi
========================
type a.txt > b.txt:a.txt
notepad b.txt # show nth
notepad b.txt:a.txt # show sth
dir /r # show hidden stream
attrib +h b.txt # hide it from dir
### You cannot see it if the settings are not right, i.e. View Tab → Options → Folder Options → View → Hidden files and folders → Don't show hidden files, folders or drives
Hide a file into an image, using Steganography steghide.
sudo apt install steghide
steghide embed -cf wheretohide.jpg -ef hidethis.txt #
steghide extract -sf wheretohide.jpg