An intriguing post by Seán Byrne on the myce web site suggests that the business version of Microsoft's OneDrive modifies files as they are distributed to Cloud storage.

Testing Google Docs, DropBox, and even the consumer version of OneDrive, Sean was able to show that files synched between local and Cloud sources were left unchanged, meaning the files that existed in both places were exactly the same. However, only for OneDrive for Business the stored files were different. Not only were the file sizes different and the modified date the same, the checksum failed. During the synching process, a Universally Unique Identifier is placed into the header of the file. Seán assumes this is to make the files identifiable to a company or user account, possibly to make them more secure, but it's not clear.

It'll be interesting to see what comes of this, or if Microsoft does address this directly.

You can read the entire account, including the tools used to validate file changes in Microsoft OneDrive for Business modifies files as it syncs.

What do you believe is happening?