The term "hdhub4u cloud" does not refer to an official product. There is no legitimate company named "Hdhub4u Cloud" like Google Drive or Dropbox. Instead, it is a marketing buzzword used by piracy affiliates to describe one of two things:
The website (hdhub4u.cloud or similar domains) does not store the movies. Instead, it indexes the cloud links. When a user clicks "Download," they are redirected to the cloud provider’s server. hdhub4u cloud
A common trick on hdhub4u cloud is a popup saying: "To play this 4K movie, you need to update your video codec." The "codec" is actually an info-stealer that logs your passwords and credit card details. The term "hdhub4u cloud" does not refer to