So OneDrive offers a bunch of storage for cheap. But as it turns out, it also inserts a unique identifier into your files that you store, which nearly nobody would notice. Either it’s a boneheaded oversight of incompetence, some workaround for legacy purposes, or some type of tracking activity. None of these is a good sign.
“Even though OneDrive for Business modified these files, it left the ‘Date Modified’ attribute in every file unchanged, so to an unsuspecting user who just checks when the files were modified, they appear untouched. For example, the Word file shows a modified time of ’16:14:14’ for both the original and synced file, even though the file sizes are clearly different. The only files that remain untouched are those that were placed in the synced folder on the original computer, so even if a user checks the files they place in a synced folder, they would not know anything is being modified unless they physically took those files to another computer with the matching synced folder to compare them.”