Two days ago, a tweet appeared in which it appears that Dropbox has blocked the sharing of some files due to copyright.
This tweet made many users wonder about the service's privacy, but they are unduly concerned.
According to the company, Dropbox only checks when a file or folder is shared without reading the files, comparing file hashes, i.e. unique digital signatures.
So, all Dropbox does is compare the digital signature of the sub-shared file with a list of copyrighted files without ever reading the files, as we see below in Dropbox's official response.
If a file is found that is subject to copyright, it is not deleted from the service, it is simply prevented from being shared.
Source: tro-ma-ktiko.blogspot.gr
